[JohnStrange]

PocketChip: only 5 h battery life, not durable, but otherwise would be ideal - but with 5h battery life it's nothing but a useless gimmick

DM42: no alarm, too limited programming (basically a HP42 clone), no CAS, otherwise it would be ideal

gemini pda: too short battery life, way too expensive

numworks: kind of cool, but doesn't meet the criteria either, and it currently still has math problems (accuracy changes with every firmware update, the least thing I want from a calculator is inconsistent floating point arithmetic)

If I knew more about electronics, I'd make my own device but my life is unfortunately too short and too busy for that. I guess you can't always get what you want. ;)