Design Sailing App

Hi, I am interested to by Garmin watch which will give me possibility to use two programs I need for sailing with my laser dinghy.
One is speed and max speed during one training. (in knots per hour which is easy to calculate from km/h).
Other is start clock from 5 min, 3 min, 2 or 1 min to 0 start. It is nice to have sync function, if I made mistake in timing to adjust to nearest minute or next lower.
It is best to have possibility to start each separately but after start that speed measuring starts.
As I am older age it is for me very important that figures are biggest possible as I do not wear glasses during sailing.
So the question is which Garmin model will give best relation: visuality against price?

If you are able to make those apps for me I would like to evaluate if I can pay your price and how we could arrange that.

Best regards
LaserD