I was looking from some advice from Matt when I stumbled upon a new project he is a part of. It is called Pear Sports. In the past I have been using Training Peaks to develop training plans. The problem is two fold. First off, it is tedious to build your own plans and second, I have to write down my intervals or send them to my phone as I tend to forget what my intensity levels are when I want to puke during a ride.
But Pear Sports downloads the training plan directly to your iPhone and Matt or another coach talks during your music play lists and tells you what zone to be in and keeps your times for you.
Best of most of the plans are free. For full functionality you need an iPhone 4S or 5. Paired with their blue tooth HR monitor, the training plan will tell you if you are above or below your zone. This eliminates having to look at your watch. Since I have an older iPhone and don't want to shell out for a new one or for the HR strap, I use my Garmin and keep track myself.