I was listening to today's No More Mondays podcast, where they mentioned being accountable. That's when I had an idea. I'm sure others have had the same thought.
This example is focused on writers, but I'm sure you could tweak it for other things. I don't plan to execute on this, only passing along the idea to you. Move it forward if it makes sense.
What if you were part of an small accountability group, where you were expected to write 750 characters a day (or whatever makes sense)? If you didn't write daily, there would be some form of accountability. Here are some examples:
You get a 'strike' or some amount of points deducted from your rating. Too many and you're out of the group.
If you miss a day, you can't post the next day until you pay some amount of money. Maybe that money would get distributed to others in the group.
No one gets kicked out or pays for missed days, but everyone pays an upfront amount to join the group. Then find some way to to reward the most consistent writers after a certain period of time.
I'm sure you can think of other systems.
If you wanted to try this out, you could setup an invite-only Facebook group. Say you wanted to do the 2nd idea above. The group would be self-regulated, and you send money to the other group members with Venmo, PayPal, etc.