This kit from Rydeen can help a lot, while backing up your vehicle. 4 sensors are installed, flush mounted, into the bumper, with a factory/OEM look. There is a small, undetectable, speaker that gets mounted up front to alert you if you are getting close to an obsticle. There is an optional LED pod, that mounts on your dash to give you a visual indication.
The PSR400R is for rear sensors. The PSR400F is for front sensors ($40 upcharge)
Typical install charges for this, is aprox $260 for labor. The sensors can be painted, to match your vehicle if preferred.