Suggestion to make it with lesser scope, but with verifiable contracts, so you can automatically verify that it was done. I'd actually use that service myself :)
For example:
1) Run 10K on Strava.
2) Solve programming challenge on Codeforces/TopCoder.
3) Pass coursera class.
4) Have X bitcoins on your wallet
5) Check-in in some specific location.
For example: 1) Run 10K on Strava. 2) Solve programming challenge on Codeforces/TopCoder. 3) Pass coursera class. 4) Have X bitcoins on your wallet 5) Check-in in some specific location.