Pepper 

We know from the trailer that she’s the one that he makes contact with, and should the message make it through, she may well be able to figure out where it came from. It’s therefore been speculated that Miss Potts will wear the Rescue suit seen in the comics to pick up her fiancé. In the comics, Tony designs the suit purely for Pepper to wear and its purpose is “Emergency Search and Rescue”, so it would make sense for it to be brought into the MCU this way.

However, Pepper herself going to save Tony seems a bit unreasonable. Surely, if she knew his location, she’d give it to someone better equipped to go and save him, rather than do it herself? But hey, it wouldn’t be the first time the MCU has ignored realism for the sake of the plot…