challenge suggestions

I have a thought for the challenge me section.

How hard would it be to throw together a 'challenge' form and SQL database to keep track?

So when you initiate a challenge, you get a form letting you describe the challenge and the goals.  Then it would have a page like a race report.  If you want to join the challenge, you hit a 'join' button which allows you to enter your pledge.  Then you could either just pull in the required figures from the training log db or have a button on the challenge page to upload your ongoing total.

It would be also kind of neat to have a challenge tracker in the training log, letting you know how you are coming along.  Maybe even a list of sucessfully completed challenges if there is space.

i would say challenges could be total monthly distance/time, or number of days of an activity (any day with time logged in an activity would get flagged).