My original plans for the system included things like reports on time usage and a system to help me calibrate my expectations for the amount of time a task is likely to take. However, I've yet to implement any of these, and honestly I'm still not sure what the best way to implement these would be. Any interesting suggestions would be appreciated; I hope to write an article about building these systems sometime soon.

Suggestion: use a reward / punishment schema to encourage completion of the tasks within the allotted time.

If you miss the deadline, you get no tasty reward for your efforts.

If you finish early, you get the reward...but you have to do intense exercise (or something) for each remaining minute.

Side effect: If you really hate exercise, you might try to prolong the time it takes to finish the task...not sure how to get around this. Removing the exercise "punishment" will encourage you to systematically overestimate times, which is not conducive to calibration. Depending on how conscientious you are, this might mean you do a more thorough job, or it might mean that you waste your time...

EDIT: Cure for side effect: Have a double incentive system in place. You get large incentives for finishing the task efficiently, and you get additional small incentives for accurate time estimation. Incentives are structured such that you will prioritize efficiency, while still attempting to maximize time estimation.