>>42961077I use one of these.
There is no cap as far as I can tell. In normal walking if you walk all day and then turn on pokemon go it'll go back some time to pick up all the walking you did.
I use one of these and have my phone rocking overnight, I wake up with about an average of 5km/hour. It's not the most you can get per hour but I'm not gonna complain about free KMs..