While I wait for the battery to charge - I'm thinking about how to make it last a bit longer.   To keep my end simple, I used a Adafruit PowerBoost board.  This also allows low battery detection and shutoff ( Not yet wired or coded ).  I can see the typical consumption runs about 50 milliamps without sleeping - but that doubles on a sample send.  

Feature ideas:

1.   Add sleep mode while awaiting a GET.

2.  Add low-batt detection and shutdown.

3.  Add charging circuit.