In the book we did not talk much about applications. There are plenty out there! Many can be really helpfull and some are just a waste of your time. I have started to blog for Iphone Life Magazines on Smartphone Coaching and applications that can help you improve your life.
So far I have done 3 posts. Check them out here:
http://www.iphonelife.com/blog/31752/use-your-iphone-coach
http://www.iphonelife.com/blog/31752/use-your-iphone-improve-your-health
http://www.iphonelife.com/blog/31752/use-your-iphone-train-yourself-feel-awesome