Some of the parts for the finalized PCB version arrived today.  Plans are to run an ATtiny24/45/85 or ATtiny24/44/84A (LCD version) from a 150mAh 1S LiPo or 3V coin cell for greater portability and smaller design

It depends on the final code size.  A QFP version ATtiny is preferred, but soldering may prove difficult.  Code cleanup is desired and plans are in place for an interrupt driven routine.  It just makes more sense.  However, the current code is fully operational.