I thinking of making a project using a RTC (which draws 1.5mA), an ATtiny85 (200mA max), and an LED (30mA). I want to power all of these @5V with a battery, smallest possible. I've seen many batteries at sparkfun which have the capacity, and using a booster, the voltage.
But, I am thinking of having the whole project in a enclosure, with only holes for switches and power plugs. Can I, and how would I, setup a circuit that would use a wall wart to charge the battery, without removing it from the circuit? (A DC jack on the side of the enclosure would be nice) (Just like consumer electronics. You can run your laptop off the battery for x hours, then you can plug it in. At this point it charges AND runs off the wall wart. I want something like this.)