LOL how can an app possibly improve its signal?
Mines on O2 and the 3G signal drops in my area or goes completely dead, but normal phone signal is fine.
Look up neckband headphones, similar to what tdubz suggested but more comfortable. I used to have a paid of nice sony ones, can't remember what model but they were very comfy didn't fall off when I used them on the way to college on my bike.