I could say over design, but zealous sounds more purposeful.
So, zealously over designed peculiar digital life-game controller here. Added a coin cell holder for a 3v coin cell (12mm) to keep the RTC clock going if power drops or is removed. Added an on-off switch(!) Added two extra components to the power management circuit — a MAX4651 for the really off situation in which I use a removable battery and insert the battery backwards, and a MAX6439 battery watcher deal that’ll signal the MCU if the battery goes below a specified (factory trimmed) voltage, pull down reset if it goes super low, and signal if it rises back above a threshold, with a bit of hysterisis. Problem was that the thing could drain the battery into oblivion which made recharge long and tricky. But, frankly — now with the on/off switch and battery back-up for the RTC, it’ll be much easier to charge over USB. I hope. Found some small LiPo batteries from an iPod Shuffle battery replacement kits, of all things. One is 230mAh
Also I found this operation:
www.synst.com.tw/english/prdlist.aspx
They sell small, flat, light LiPos with decent capacity (160mAh+/-), but much more expensive and harder to get.
Curious about what’s what? The Flickr page has “notes”.
Update. The iPod replacement batteries work great so far.