Most cellphones on the market can do a function called fixed dialing this enables you to only allow certain numbers to be dialled. You lock the phone using pin 2 and problem solved.
The actual idea of the phone is that my mom hasn't been feeling well, and her blood pressure is all over the place. Given her history I thought this kind of phone would be perfect because god forbid in the case of a heart attach or stroke, she can push just one big button and I will be alerted and notified where she is via GPS.
Vodacom has a device which serves as a personal tracker and a phone as well. Depending on where you are in JHB i would suggest you go to either Vodaworld or any Vodacom accredited outlet.