If it is not already incorporated, the most useful function I can see would be adding a Tacking Ratio/Start Sequence to establish ones start, a function my Timex Victory watch used to perform before it died.
One sets the "start time" and then near the start establishes a "tacking ratio" by tripping a timer as one crosses the starting line at the reciprocal of the preferred heading at the start, sailing along the reciprocal of the first course line for a time, tacking back toward the start line and tripping the timer again and then sailing ones preferred heading/course at one's best speed for the start and tripping the timer a third time as one reaches the starting line. With this, one has a total time elapsed, time heading away and time heading for the start which are used to establish the taking ratio (e.g. one might sail "away" from the starting line for five minutes and back for seven minutes, hence ones starting run is 5/12ths or 41.67% of the total elapsed time).
With this, near the starting time, when one begins ones final "Starting Sequence", one trips the "Tacking timer" as one crosses the starting line sailing away from the course for the last time before the actual start. Based upon the actual time remaining to the start, the timer sounds a warning a minute or so before the final tack back to the start and then a "tacking signal" when one should make ones tack. With that, one tacks and makes ones best speed back to the starting line and should hit the line at the exact moment of the start assuming the winds remain fairly steady.
For example, if one establishes the 5/12 tacking ratio, above, and one begins ones "Starting Sequence" 8 minutes before the start, as one crosses the stating line one punches the "Start" and sails away from the starting line for 8 x .4167 = 3 min, 20 sec. The "Start Timer" sounds the tacking warning at 2 min 20 secs and then again at 3 min 20 sec. One tacks and sails back to the start at ones best speed and should arrive at the line in 4 min 40 sec or right at the "Start" at ones best speed.
One can do the timing described above with a stopwatch but in a race, it almost requires a dedicated tactician/navigator with that job only and not preoccupied with "driving", trimming, or crew management.
Adding that to your App would be a very worth while effort.
With StartLine you don't need to do the tack ratio thing. You have a timer that tells you how long it will take you to get back to the line. No matter where you start from, what traffic you get caught up in, what direction you are going, you can tell when to turn and head back to the line. For example, if you know it takes you 20 seconds to turn your boat and accelerate, just head away from the line until the "time to burn" readout reads 20 seconds, tack, and go for it.
This is the beauty of using the target boat speed rather than actual boat speed and direction that most apps use. If you use actual boat speed and direction and are heading away from the line, these other apps will tell you that it will take forever to get to the line as you can't get there on the course you are on. With StartLine, you enter your target boat speed either manually or automatically and then all times are based on the speed you will be traveling when you head back to the line.
I have tried the tack back technique and other boats always mess it up. That was one of many things I tried before writing StartLine.