Aside from the other reply, pi makes it _really easy_ to build your own usage tracking and limit machinery. I would normally advise against such efforts for a

Aside from the other reply, pi makes it _really easy_ to build your own usage tracking and limit machinery. I would normally advise against such efforts for a variety of reasons (such as inaccurate tracking, etc), but specifically under pi, this mechanism has been extremely well behaved and accurate for me.