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Comment by mark_l_watson | Hacker News Reader

He brings up an interesting problem for smartphone (or any cellphone) use. I know I will never see this as an available product but I would like: something like my Apple Watch that had a simple hardware switch that would turn off cell and GPS connectivity. Then I could occasionally check my messages or missed calls but most of the time have communications turned off. Note that the Apple Watch has an "airplane mode" that turns off cell connections (I think) but not sure about GPS.

I have read about Linux cellphones that do have hardware cutoff switches so that would be a good way to remain private most of the time.

EDIT: it looks like going to airplane mode also disables GPS: "when the user activates airplane mode, they will disable Bluetooth, GPS, phone calls, and Wi-Fi" nice!!

EDIT 2: starting with iOS 10, GPS reception stays on in airplane mode

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Is this a massive misunderstanding of GPS? What are you hoping to do here?

GPS is a passive antenna / receiver. You don't emit anything with GPS, you just passively pick up signals from GNSS satellites. You could "turn it off" by unpowering the GPS receiver, but there's little benefit there, and that may not be possible because most of these are soldered directly to the mainboard for power efficiency reasons. These embedded receivers barely use any power whatsoever, and if your cellular / WiFi is already off, it's certainly not transmitting it in real time. If you want to stop location logging you would need to opt out of location logging. I don't know if that's possible with Apple Watch products, but turning GPS "off" doesn't tend to make a lot of sense in many contexts.

Turning GPS devices off could allow you to avoid attack over RF against GPS device firmware. This 2012 paper details some possible attacks, including a bug that lead to the GPS device continually rebooting.

http://www.locata.com/wp-content/uploads/2013/08/GPS-Softwar...

when GPS is on, my phone uses more power. maybe because there are apps running tracking the GPS data.

GPS itself doesn't transmit. but apps log the data and they to the transmitting.

my main concern is any apps that need location from time to time. there is a permission to allow access to location data, but switching gps off does not toggle that permission, and apps still track location through wifi and cell locations, and i can't find any way to toggle that.

I don't know about Apple watches, but I do something kind of like this on my Android phone using Tasker. I have it toggle airplane mode for 55 minutes at a time, "waking up" for 5 minutes every hour to send and receive messages. Operating in this mode reduces my digital footprint and has a fantastic effect on battery life, but it's kind of a drag for people who want to call me. My dream phone would have a built in one-way pager radio to alert me of incoming calls and would only connect to the cellular network if I chose to accept the call.

You don't have to put airplane mode on. You could just disable all data instead (LTE, WLAN, BT). This will disable all radios except phone calls. That way, incoming calls still work.

On my Samsung S8, airplane mode doesn't disable GPS. It doesn't need to (GPS is a signal that your device receives) and I'm glad that it doesn't. On budget flights where I've been seated near the window I've sometimes managed to see where we are using GPS.

on lineage airplane mode turns of everything, which i like to save power, but it also allows me to turn stuff back on individually, including wifi (useful for inflight wifi) and GPS

correction: it turns that i was wrong and airplane mode on lineage does not turn off gps.

You can do this by putting a phone in a faraday cage. A quick search shows various wallet-sized poaches available, but I can't vouch for their effectiveness. I wonder why they're not more popular, nor even mentioned, among all the talk of "hardware switches".

Not a radio engineer, but it's the shape of the Faraday cage that matters I think, not the size. The required shape most likely depends on the wavelength, as the idea is to distort the waves... Basically if your grid is too tight (ie a sheet of metal) the waves keep their shape, but if the grid is too loose, the waves just pass right through.

That's what I've been told by fellow meshnet hobbyists anyhow ;)

I have read that if its not in airplane mode, a phone will consume more power trying to establish a connection than a phone that has good signal.

Having a hardware switch is also just more of a usability thing, make it a simple choice to turn off the radios/notifications, don't make me go into settings to have some peace and quiet...

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