DownwardDog
Riding a Brompton with a power meter.
I don't really get why these things are devices rather than apps. Everyone has a smartphone now... Surely just buying a handlebar mount would be cheaper.
Apart from the battery issue phones don't have ANT+ so you can't connect power meter, HRM, Di2, etc.
Also, another endorsement for the Wahoo Roam. They are way better than any Garmin. They also don't have Garmin's warranty policy which is basically: stick your broken computer as far up your arse as you can get it.