External Battery PLus charging and juice alerts

Anybody’s running their beaglebone off of a external battery and a circuit that can charge the same battery and also at the same time read from the circuitry’s IC that how much juice is there on the battery?

Can you guide me on the correct battery capacity type I think going with a 2Amp Lipo will give me around 1 hour of working

RAVPower 14000 External Battery Pack http://www.amazon.com/RAVPower-External-14000mAh-Incredible-Motorola/dp/B00EHEEFWY

So costly, I’m eyeing this >> https://www.sparkfun.com/products/11360 have a look please and tell me,

I think at 2 amps it will just give 3 hours of backup at max. but I’m fine with it because also need to consider the cost!