Something to optimize battery, screen (only really need Eink or something low power), and other aspects for that mode of communication.
Maybe I will sit down and see if I can design something myself.
I was half-interested in buying a pair of these to try that with. However, an honest assessment of my ability to commit and complete it made me skip it. If this is successful and a second device (or less expensive version of this) comes out I'll reconsider.
A smart watch gets me most of the way there.
I can still get and send text messages to my wife, and look at our shared grocery list, and do simple technology-assisted things. But I'm free of the temptation to look at HN, or doomscroll a news app, or participate in similar over-distractions.
The Hellschreiber was invented in the 1920s, and the "protocol" is still in use today. CW transmission of symbols (Morse code, for instance) began around 1913, this is after, of course, spark gap transmitters (such as those used on the Titanic) and telegraph.
I personally cannot understand or use CW/Morse, but i have radios and software that do it for me. There are extremely tiny, battery powered CW radios, usually costing $50-$300. If one can use CW and understand it, that's wireless, telephoneless communication. Hellschreiber, though, requires a display (or clever OCR, due to the way it is transmitted over 3 identical horizontal lines), but a chiclet style keyboard could be used.
Unfortunately i don't know of any consumer-y way to do any of this. APRS(c. 1984) 100% could do tiny, text-only messaging, and in fact does already, but requires licensing. I can send a text message to anyone at an internet connected device with a screen, or anyone, anywhere with a radio that supports it. X.25(1976) also exists, as does PACTOR(1991), both of which in theory don't need much more than a display and a way to input characters.
Back to my point, though, telegraphs have existed since before 1792, and the idea was to be able to see semaphore further away. Electrical telegraphy(1809) was first 35 wires in 35 tubes of acid and the operator had to watch for bubbles in each tube. But about 110 years after that, teletype became more prevalent, and there we have Hellschreiber.
Just a quick remark, I believe Hellschreiber is transmitted as a single line, just displayed as multiple in order to get around the skew caused by timing differences.
Today's radios, combined with FLOSS (or at least 'source available') software can get timing synchronized within 20ms, including the delay in actually getting the RF out of the 'antenna' - pci latency, soundcard buffer latency, radio soundcard latency (if you're using a radio that connects via USB, see ic-7100 for example). When I use WSJT-X, which is "weak signal" software, i routinely notice less than 1s timing deviation median. WSJT-X relies on the system clock that the software uses to be accurate, as transmissions start at published times - like exactly on the minute boundary, :00. all reception reports include the time delta.
As another data point, slow hell mode uses 30hz of bandwidth, and i have used kiwisdr websites to 'hear myself' nearly everywhere in the world using slow hell mode. No one else is using this mode, so i generally have to use kiwisdr to test different modes, antennas, and radios. Another open source project, iirc.
• The app is an email client, so anyone with an email address can reach you through it, and you can send email through it;
• but the email client is a proprietary one, associated with its own special email service provider (so you have a separate email address with them, and if you want to receive your regular email there, you have to set up forwarding);
• and the email servers that this email service provider runs are special, in that they will deliver others' messages sent to your address, to your account's IMAP inbox, only after a 24hr delay; and they will forward the messages you send through the SMTP server, out to the next server in the SMTP chain, only after a 24hr delay.
Given such an app+service, people could still reach me, but nobody could ever reach me synchronously. And I couldn't reach them synchronously, either.
It'd be like the feeling of latency that comes from corresponding using physical letters, but with those letters happening to arrive wherever you are, rather than at a postbox. (I guess most similar to corresponding using letters when you're at a war front. A courier walks up to you and hands you a letter, sent from home 24hrs before.)
Given the delay, there'd be no real point to messaging anyone more than once a day. I'd write an e-letter to each person, updating them on what's been going on with me, and then I'd turn my phone off. No point in wasting battery on it when any message is going to be at least 24hrs old when I receive it. May as well just check it in the evening, or the next day.
If I see or hear something nice, I can take a picture / record a voice memo of it with the smartphone per usual, and include that picture in the letter I write that day.
I could even vlog, I suppose. (Do you call it vlogging if it's done over email instead of over the web?)
I could still subscribe to newsletters.
And I could ask people to forward me clippings of interesting things they find on the web, as if it was 1996.
But doomscrolling on social media? Impossible.
Acting as a remote IT helpdesk oracle to diagnose some failure someone's having? Also impossible.
If someone really needed a specific, single question answered, they could ask me, but only if they don't need the answer urgently. Better to just ask someone else, unless they don't have any better option.
But having an "evergreen" conversation about an interesting topic would still work just fine.
Heck, even participating in a Play By Email (PBEM) tabletop RPG — do people still run those? — would work fine.
So it would really need to be a special single-provider email client app, like Gmail's mobile app is. One that has no ability to talk to any other server than the 24hr-latency one.
And at that point, with an app like that published in real app stores, the 24hr-latency server backing that app would become a real production capital-S Service with lots of users. One I'd rather someone other than me was running.
I mean, even if you go to great lengths to choose to subscribe to a particular email service that does this and choose to buy a phone that only does this, an employer could still demand you use a regular phone or regular email for correspondence or choose to not hire/work with you. I really can't imagine most people would be like "huh your phone only works in this one very peculiar way, I guess there's just nothing else that can be done about that." They'd just tell you to get a regular email.
To other people there would be little difference between you choosing to use a service and device like this as you only using your email client once every 24 hours. Its ultimately the same thing: you're choosing to put yourself in a position where you can't be reached for 24 hours. Shifting the blame to some 3rd party isn't really effective when you theoretically can change back and sign up for a regular email account at any moment.
Don't get me wrong, I'm not demanding you live your life any particular way. Personally I don't care how you choose to live your life and I agree we could all use some time to detach from our always on always connected communicators. If you only want to be able to communicate by a 24 hour delay, go for it. Just don't expect everyone to suddenly be OK with it because you went out of your way to choose a service provider that facilitates that. I imagine you will encounter a good bit of friction doing it with the way society works right now.
Think about it like: I'm already on vacation, that my boss three levels up (CEO) approved, including explicitly approving / encouraging-as-company-policy my use of this device/service during my vacation. Now boss-two-levels-up (some VP) is trying to cover their own ass for something they didn't do, by telling me to do urgent work during my vacation. The only way to actually get them to go away in a way that doesn't result in awful office politics happening to me, is to make it technically impossible for me to be reached, or for me to do synchronous work. Thus the device, and the public/institutional knowledge that I'm only reachable through such a delayed mechanism.
That way, rather than me having to make waves (which could get turned around on me, since I'm not there to defend myself), the VP would have to make waves about me not responding — which would expose publicly to the rest of the company the fact that they're trying to make me work on my vacation, and cause the CEO to come down on them. Very likely, they'd realize that, and just give up on the idea of shirking their responsibility off to me.
(This is all hypothetical; I don't even have a boss.)
This is also a good reason for putting a vacation auto-responder on your email/chat. You then have a documented paper trail that you're not supposed to respond so they can't later argue they thought you were shirking off work.
But once you consider an email client, it turns much larger.