Tempo for Apple Watch

Would love the ability to be able to control the tempo of the songs on the apple watch, the ability to be abel to control the music with the watch is amazing as a dance teacher, but the only thing that would make this application even better would be able to slow and speed up the tempo. just a simple + & - or a slider would be an easy and amazing addition. would also help with DJing as it helps meld temps nicely when switching tracks