Timely subject. Just yesterday I ordered another Nokia Windows phone. The Nokia 521 running windows 8.1 that has been use for 7 years has a bad battery and a cracked case. It fits into the seat pack very nicely as it is small. Runs on T Mobile. Got another Nokia, but it is a 950 so larger than the 521, but runs Windows 10 and will just fit in the seat pack.
Chose Windows phone because the operations are simple and easy to see, plus reconditioned it was only 55 dollars. Should be good for a few years bouncing around in the seat pack.