How can i implement a listener for the gps?

I have an iPad app and wish to call a function every 0.1 miles I travel from a certain x start position . How can i imple开发者_Go百科ment this listener ?

Take a look at the CLLocationManager docs and a tutorial is here.

Disclaimer : I haven't read through the whole tutorial; if it's not good enough all I did was google for 'cllocationmanager tutorial' ;)