A few quick thoughts-
- In no way does any ap even come close to resembling FAT. There is one that claims to do so and it is essentially a piece of garbage. So, get the automatic timing/photo finish concept out of your head. Nothing but an FAT system, costing usually $8k-15k will really do the trick.
-There are very useful timing aps. "Chronotapper" for distance races or cross country races is the equivalent of a printer watch, which usually cost $300+, but never runs out of paper or batteries. It will list in order as many splits as you want, plus you can email from the ap and then print. You can easily scroll through the file and you can save the file on the ipad. Of course, a $40 timex ironman can do 50-100 splits too.
-There is an ap just called "stopwatch" that allows you to take and view splits from 6 or 8 athletes at once. You can name each stopwatch and all of them are displayed on the screen at once. The splits can be emailed, saved, etc. I find this ap to be the most useful when coaching at a meet and needing to take splits for multiple kids in the same race. It's WAY easier than doing it with a timex and writing them down.
I don't know much about filming athletes using an ipad, but I'd be careful with that anyway. You'll get DQed if you do that at a meet, but I could see its usefulness in a practice setting since you could immediately show them their flaws on a pretty nice screen.