Check out Web Metronome .com - a free online metronome or any of the free metronome apps that have a visual aspect to the click track (Tunable is the app I use and recommend), every artist of any skill level can benefit from practicing with a metronome / click track, and you specifically sound like a visual aspect to that would help because it will keep you in time as you record your raps. I still want to hear one some day, PM me a link sometime