My family uses Find My Friends on iOS a fair amount, just to keep up with who's where. I'm the only one who might take a bike trip, and I'm the only one without an iPhone, so that particular use case hasn't been tested by us, but in general it works very well. Of course the phone needs to be on and connected to a cell network, so it doesn't work in some remote areas. And when I find that I'm in a spotty coverage area, I either turn the phone off or put it in airplane mode to conserve battery, so Find My Friends, or any service that relies on cellular data, wouldn't work in that situation.