timbosan:
The battery in the wireless unit is rechargeable - you just take it off every so often (every few months) and charge it via USB. Takes a few hours. Unless you have compatible wiring already outside I recommend the wireless.
Sorry I didn't mean Eufy has a smoke alarm - they don't that I have seen. I have Nest Protect units - the thread I linked to was about smart smoke detectors generally.
True re recharging. We do have doorbell wiring and I see the wireless option can be wired anyway.
Are you happy with the Eufy gear?
