Looking for an iPad music app that knows how fast I'm going

I ride a 2011 Harley Davidson Softail Classic, I removed the windshield in which I replaced with a fairing. I now have a great speaker system, I've incorporated my iPad4 as the GPS, music, weather, etc. Here's what I am looking for and hopefully someone has a solution. I am looking for an iPad app that will automatically adjust my iPad volume as my speed accelerates the iPad music volume increases and when my speed decelerates my iPad music volume decreases. Currently regardless of what speed I travel the iPad music volume stays constant. This needs to be done automatically so hands stay constantly on the handgrips and my eyes stay focused on the road. I've been informed that android apps has this application yet I haven't been able to find one for apple iPads. If anyone can assist I would greatly appreciate this.

I've created a video which I've placed on YouTube, the Title of the video is "Bill's iPad app for motorcycle"