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Comment by lxgr | Hacker News Reader

> Imagine like, an airtag, but the ID only needs to be 1 byte long,

Well, then you could only ever track 255 different tags :)

AirTags are already pretty minimal. Their battery lasts about a year, and I imagine an open source equivalent should be possible to build for under $5.

This is purely guesstimated based on the fact that I have a couple of Bluetooth LE thermometer/hygrometers that cost me about $3 a piece that last about a year on the same battery (CR2032) – and these run custom firmware and need to run a display and data logger (to on-chip flash) as well!

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A year is a long time, but you can also get a CR2032 to USB converter and use that as a constant power source.

Why? If you're using your smart tag to track your car, you can hide it somewhere deep inside and connect it to the vehicle's battery so it always has power. Then you never have to worry about changing batteries.

Apparently there are Find My compatible generic tags coming out of China already, and they cost less than $5, shipping included. I say apparently because I’m still waiting for one to arrive and test.

Interesting! I would have thought that Apple would add some sort of tamper-proof hardware authentication mechanism, given how expensive and privacy-sensitive AirTags are.

They opened it up to avoid anti-trust issues.

This sounds awesome - got a link?

https://a.aliexpress.com/_mrvl4Xq

Interesting. Although your link is 11.70$ with 50% off for me, but if you search for “find my Apple” you get many more results with lots of options around 5$

They seem to come up in the home page deals section quite often for me. I grabbed a couple that were $3.50 a pop, and so far they've behaved exactly like an Airtag (albeit with a worse speaker)

Neat. Are they also water resistant (splashes/rain)?

That link is less than 2usd (1.62chf) for me. I’ll never understand Ali’s pricing.

fyi: apparently that's only a welcome (e.g., first-time user) offer. As soon as I logged in, it changed the price to ~11usd per piece.

Yeah, typical aliexpress misleading BS. I have yet to buy something on AE and 1. Pay the price initially shown (it’s always more) 2. Actually use one of the dozens of coupons it assaults me with every time I open the app.

You'd just have to have IDs repeat, and software that could tell the difference based on signal strength. If you have two on the same ID that have different RSSI, show them as two tags.

You'd have to do some guesswork though to figure out what's going on but it would be better than nothing, and you might be able to get the size down below what CR2032 allows.

But why only send a single byte if you can send a full UUID within a rounding error of the same resource usage?

If you want it to be compatible with most smartphones, you'll need Bluetooth LE anyway, and that already uses at least 10 bytes on header fields for broadcast packets.

I suppose it is effectively a rounding error unless you change the actual protocol.

I wouldn't be surprised if there was some trivial way for the manufacturers to add ultra low speed non-bluetooth data to the Bluetooth chips though, so you could have 2400 baud IDs with microwatts of power.

But it's probably not worth it since I suspect the real power drain on airtags comes from the high update rates and maybe the 2 way communication.

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