>>284525598
>>284525619
>>284525932
So, what amount of mAh sould I aim for, for a powerbank for each tracker? Say, to have 8 hours more of battery life.

More is better, but more also means it'll weight more and thus make wearing it uncomfortable. I don't see anywhere how much power these trackers consume, and the trackstrap-trackbelt-thingy doesn't say how high the capacity is, either.