I require this for controlling irrigation run times. The time selector almost does it except for the AM/PM box. For example, if I want 10 minutes I can put this into the time selector and leave it at AM and I get what I want - perfect. If however PM is selected I get 12 hours and 10 minutes, not really what I want and a little dangerous.
For me at least the solution is simple by providing an option on the time selector to show/hide the AM/PM box. This would in effect turn it into a duration selector. Actually a 12/24 hour option would probably work.