For the past 2 years, I've been struggling with a fairly simple problem. Whenever I would get ready to run a race, whether it is a 5k or a marathon, I would also frantically struggle at the end crafting the perfect playlist. I wanted a playlist that fit parameters for that race - a 5k is quick, short, and needs to be pumpup music the whole way while a marathon is a long haul, and you need more a variety to sustain you.
This idea has been on and off for a bit but this past Spring I've finally sat down and tried to make it happen. Harvy is a simpler version of that idea though - put in how long you want to workout for, how long your run is, or how long you want to listen to music for, and a playlist will be generated to match that time. Going for a 25 minute run? Receive 25 minutes of music to help push you each step of the way.
Check out the site and leave some feedback. There is still a loonnngg way to go, but this is a basic beta product. More features are on the way!