You can swap a coin-cell powered design that uses one-use Lithium 2450 cells for this rechargeable cell. This battery is like a little Lithium Ion battery, but in coin cell shape. It doesn't have a huge capacity, only about 120mAh, compared to the 600mAh common to primary non-rechargeable cells.
There are a few things to watch out for when using these batteries:
Additional safety notes: Do not use a NiMH/NiCad/lead-acid charger! Also, do not abuse these batteries, do not short, bend, crush or puncture. As with all Lithium ion batteries and with any power source - they should be used by experts who are comfortable working with power supplies.
Lithium Ion Rechargable Coin Cell Battery - LIR2450 (16:34)