Using icloud.com, she can track you with the Find iPhone feature. The nice part about this one is that it requires absolutely nothing from you. No need to hit "start" or run anything on the phone. Glympse (I spelled it wrong the first time) also sends a link that can be used on a computer or any other device. No app required according to them. I have never used mapmyride's tracking feature (didn't know it had one) but assume it is much the same. The down side to the two of these is that, I believe (not 100% sure), it will run your GPS the entire/most time you are out which could hurt battery life, whereas Find My iPhone will have no impact. That could be important if you are out for a long time. No cell phone is probably worse that not knowing where you are.

One last thing, and I am sure you already know this, but I always tell my wife which route I plan to take that day and generally stick to it. I even leave a course map up on the computer if its one she does not know. There are many places I ride without cell service, so if she were to ever lose track of me and not hear from me, at least she would know where I was supposed to be.