[networked]

Despite much of it being proprietary Nokia's S60v3 platform, a Symbian derivative, was/is if not easily hackable (due to the whole certificate business) then at least very easy to write basic apps for. This is thanks to a great Python interpreter [1]. With it I built an RPN scientific calculator with a custom GUI and years later a remote control program for Motion [2] in about an evening each, including (re)learning the API. Thanks to PED [3] I was even able to write small text-based programs on the device itself (though I'd recommend against that if you don't have QWERTY phone; programming on a Nokia N73 was hard enough back in 2007). If you happen to have a phone that runs a variant of Series 60 give Python a go.

[1] https://en.wikipedia.org/wiki/Python_for_S60. The final 2.0 build sadly broke some networking code. There were very few people complaining, so it didn't get fixed. I suggest using version 1.4.5 instead if you choose to play with it.

[2] http://www.lavrsen.dk/foswiki/bin/view/Motion/WebHome

[3] https://code.google.com/p/ped-s60/