For PDA you could use Embedded Vb 3 (eVb). Isn't supported by MS anymore, but works pretty well, and is basically a cut down VB for free. Plus there are books on it (I know cos I've got some of them). Think NSBasic expanded on it, but costs money. .NET costs money too.
For mobile phones you could try mobile basic. [href]www.mobilebasic.com[/href] Last version I tried (about 1.7) even allowed you to type code into your phone. Was a bit conky to do this (instead of uploading from PC), but pretty cool. Probably better if you have one of those full keyboard mobiles, such as that nokia thingy.
Cheers
I am 99% probably lying in bed right now... so don't blame me for crappy typing