Do Mobile can Transmit Signal ?

I am from Electronics background, but i am working in an IT Sector. Recently i came with a doubt/idea why mobile cant transmit the signal. Imagine, if mobile can transmit and receive signal,

• then we can ableto reach a person even in the remote area. 
• GPS can work effectively. 
• Installation of Towers can be avoided

Y this can be done

• If a technology name Bluetooth can allows you to transmit your data from your mobile to another withing a distance of 2 meters. why cant be there some device installed in the mobile to transmit the signal between devices within availability of 100- 500 meters .
• Installation need for towers can be reduced - so this idea is a cost -effective thing

Y this cant be done

• Might be the transmission of the signal needs extra power. So the battery of the mobile might get emptied easily. 

But apart from battery issue , i think its a better idea. The readers of this article, should comment on this.