Sending command via phone or mobile phone
You need some kind of DTMF decoder.  If your mico has a DSP core it would be pretty easy to do on chip.  Otherwise you will need some external hardware to properly handle it.  A quick google search turned up this project with an ATMega: http://www.uchobby.com/index.php/2007/09/30/phone-to-microcontroller-interfacing-with-dtmf/

Another issue is if the mobile phone will correctly pass DTMF tones.  I don't see why they wouldn't, but its always a possibility.