Or 2 metres from the window a mile from Hammersmith. If not for WiFi calling I'd have to leave my phones on the windowsill.
Might be more reasonable to use higher bandwidth, lower latency codecs over bluetooth as well?
Decide which one is it.
PS Motorola talkabout T62 or T42 - small, light, reliable. Retevis h777: sturdy, reliable. You can just drop them in the bag.
Purpose-built hardware is Class 1 (much stronger, 100 mW/20dBm vs 2.4mW/4dBm), and they can use sophisticated protocols to keep the connection stable. And that's Bluetooth.
If they're not playing Bluetooth but go general ISM, they can emit whole 1W on 2.4GHz or 915 MHz.
They're not really alike.
For one rider to one rider you can get a very decent set well under $100 (Lexin b4fm, FredConn, even Thokwok is well reviewed).
I wonder if there's a home lab / self hosted solution for this.
I don't think so.
Also, I could see it as a useful tool in emergency situations. But a lot of people would need to use it to be actually useful.