Open Question: Looking for a pbx system that uses cell phones as extensions.?

what im looking for is that when you call a land number it will give you a message such as " You have reached the offices of such and such press 1 to Connect to Smith 2 to connect with Jones" But i want it to transfer to cell phones. I know it will take two or so phone lines but that's ok... I don't want a virtual number...I want it to use my analog number. Im searching pbx systems but i don't even know what this feature would be called.