You don't need an expensive power meter to track your progress.
For short efforts like the flying 200M, (generally speaking) max speed is directly related to the fastest time. If you don't have a friend to time you, just use a $50 Cateye Strada wireless (or similar) and log your gearing and max speed. There are plenty of free workout apps in the iOS/Android app stores. Just create a custom exercise and log your max speed and gearing from every effort. MAKE SURE to reset after every effort!
However, if you can afford it, get a head unit that will record the entire workouts for download and review like the Garmin 500 etc...
If you want to check your form or want splits as you prep for a big event, use an iPod/Android tripod and record yourself:
When you download the video at home, play it and use your stopwatch app or the time markers in the video to get your splits. Try to record all of your major and minor TT events for review later. You can calculate your average speed for each split based on the time and distance traveled. You can use my app to calculate your cadences, too
