> 5.  How are they looking as for as power usage is concerned?  (My
> application is in wearable computing...)

I can only really answer question 5 from our experiences here at CUED.
Typical current draws are 100-200mA, and we're developing three
different battery technologies:

For robotics within the department, ~2.5AHr batteries at a nominal 12V:
  - NiMH pack - lighter, but considerably more expensive. We're
currently experiencing problems with our charging circuits.
  - Sealed Lead-Acid - heavier, but around 1/3 the price of the NiMH
packs. I've got a working demo sitting on my desk, and am currently
routing a small PCB.

For the PDA being developed, we obviously had to go with Li-Ion for the
weight saving, and - for convenience - I selected the Nokia BL-5C
battery - 900mAHr at 3.7V. The beauty of these are we can run them in
parallel to get almost 2Ahr, and they're easy to charge -- either in a
Nokia desk charger or a phone like the 6230i (Which both I and Chris
Jones have)

I hope that's of some help - I imagine for wearable computing you'd want
to save as much weight as possible and go with Li-Ion (even the NiMHs
weigh in excess of 0.4Kg


Mike Morley