I have found a way to do this, if you use an email to SMS provider such as http://www.24x.com or http://ws.textanywhere.net in the UK (both of which cost some money but not a lot and pay as you go £10 to £25) you can get an email to SMS service that gives you a dedicated email address that you can put in the email trigger for the Geo Fence.
Both the above providers offer a time limited free trial, the setup for both is a little different but both work.
However to extend the discussion a little. I was investigating this to try and set up a cheap security tracker for my caravan when it is in storage, I am now a little concerned that one having read the www2 site that the tracking is real time -2min and the other issue is that the system would be stationary "I hope" for 6 months or so and appear to be inactive so would the account get terminated.
I do not think the Proffessional Reperion is what I need but I do need genuine real time tracking for my idea to really work, perhaps a basic plus type offering.
Mike any comment
The best things in life are free!!!!
Or at least very cheap!!!!