This is definitely something I'd be interested in! The chrono would be a good tool for troubleshooting. And the shot counter would be really useful - especially for us GBBR users with 30 rounds in the mag.
It'd also be really useful for training to keep track of your shots. You can practice trying to get a feel for how many rounds you have left in a mag, but you can never really be sure if you're keeping an accurate count, until your mag runs dry. Having a HUD would help that.