Endless Pool Swim Spa Workouts

I'm getting an Endless Pool Swim Spa in a month and I'm trying to figure out how to do a sequence of intervals. My example sequence is 8x50@1:10, 2x100@1:20, 1x200@2:25, 4x50@1:10. I'll have the Fit@Home app to program the intervals and speeds, but I need some sound queues like a starting gun to start the interval, a sound effect to give me a warning 5 seconds before the effort is done, and some intermediate beeps or metronome ticks to count off every 10 seconds or so. I don't have any watch. I will have integrated Bluetooth music. I'm thinking about using Audacity to develop an mp3 sound track for my intervals, counting off the metronome ticks over a 30 minute set, and applying sound effects for start and stop warnings. I can also add musical accompaniment from my mp3 library. I'll have to sync the Fit@Home start with the MP3 start. Problem is - when I get faster, I'll have to regenerate the tracks. Anybody done anything like this? Any ideas? Thanks! Jacob