The SoShine SC-S1 Universal Li-Ion 2-Channel Digital Battery Charger looks ok and I'll probably buy one at some point.
It's interesting that it has different amps for different channels
Channel 1 (slot 1 and 2): 1*500mA or 2*250mA charging current
Channel 2 (slot 3 and 4): 1*1200mA or 2*600mA charging current
The minimum current output is 500mA and the max is 1700mA.
I'm not sure the 12V car adaptor will be a great deal of use as you'll need to have the engine running to supply enough power (if you want the car to run later).
I guess you could charge your batteries for 'free' on long journeys....
