This was great. I say "was", because since Friday it no longer works. 1 hour is now back to $1 :( When I went to use it on Friday afternoon, it was showing as free, but when I went to confirm, it gave an error, and the freeness went away.
I've de/re-registered, reinstalled the app, restarted my phone. No dice. I'm on prepay, and even had a pack renewal on the weekend (waited to see if that would fix it). Using Android.