You just need a phone and a daily click
The community around it seems to be growing though, so who knows what the future holds for that one.
You need an invitation code to join and I heard "Flipstar" is a good one to use ;-)
"Pi is a new digital currency being developed by a group of Stanford PhDs. For a limited time, you can join the beta to earn Pi and help grow the network. To join Pi, follow this link https://minepi.com/Flipstar and use my username (Flipstar) as your invitation code."
