PIC && WiFi suggestions

[dhouston]

A couple more points...

What voltage for the PIC? BR batteries output 3V.

A few years back I used two BR coin cells (6V) with a 5V LDO to supply the PIC as well as sensors read by ADC. To monitor the battery, I read the LDO output with an ADC channel while using the battery voltage as Vref. As long as Vbat>Vreg the ADC read less than MAX and the battery charge was >5V. As soon as dropped below 5V, the ADC read MAX. This would occur very near end-of-life. Here's a schematic.