Sending data when it is different than previous measurement only

Rules for sending data:

for battery charge level, every time it is increased or decreased by 1%,
for GPS location, e.g. when there is a difference of more than 10-15 m from the previous location,
at rest (zero speed or when speed reading is impossible on a given device) -- never,
when moving (non-zero speed) -- send at the frequency set by the slider, ignoring whether something has changed or not (because if there is a speed, there will be almost certainly any kind of change).

the-jamb / gps-protect