A recent story in the news here in Upstate NY led to this idea.
An elderly couple lost control of their car on a remote section of interstate far from local cell coverage area. The gentleman froze to death and his wife barely survived the 36 hour ordeal. They had a fully charged cell phone and were
within 60 feet of the road but due to the terrain and the snow they were not seen.
I propose a cable composed of numerous single, cellular antennas spaced closely together in a long string. These would be connected to small repeater modules at the required intervals for good signal transmission in the central line. Upon detecting a phone operating in emergency/911 mode(a very simple software setting) the cable would receive the signal and relay the call or at least relay its location within the cable if normal bandwidth cannot be achieved(based on the interval and the number of antennas that detected the signal). This would allow SAR personnel to be aware of the approximate location of the transmission even if a complete call could not be achieved.
The big advantage of such a system is that the cable could be manufactured very inexpensively then rolled into a groove in the pavement along the edge of the road. This would allow for desolate stretches of road to have emergency cell system access for a minimal cost without unsightly towers in wilderness areas, or areas where terrain makes towers inefficient(mountainous).
A more developed version perhaps could handle regular traffic on roadways.