Thanks for that, it's very much appreciated. Playing with my own firmware is out because I don't have the spare time :-)
I can use a micro to handle power management; an attiny should do the job. I was hoping for a solution that used discrete components though.
I'm doing a project that will be battery powered from a less than 700mAh battery for periods of about 1 hour at a time. It will be completely sealed and inaccessible so the battery will remain connected all of the time and it will be charged either with a usb cable or via an inductive circuit.
The intention was to have a single momentary push button to turn it on (if there was enough power) and it could turn itself off if the battery dropped too low or it was shutdown via the wifi gui.