I've got a Maha just like DM td5 for AA/AAA recharging on the go

for specific camera/laptop/phone chargers, most (if not all) charge below 12 volts DC, thus a DC-DC convertor is your best bet - more efficient, lower cost.

I got mine from a clearance sale from a remote control car shop, it has multiple user selected output voltages and can push out up to 1, 2 or 4A DC per circuit (it has two circuits) for charging.

PS - Simon's unit looks the dog's danglies!