When installing a new stereo system recently I also fitted a £20 maplin parking sensor. When installing I had plenty of choice to run cables etc as all trim was out anyhow. I also realized at the time that an instal would not take long to do with far less disturbance of the trim. Boot three of trim sections and cockpit can be run all through the three plastic guttering sections. Once installed I really do use it and find it to be a massive boon when parking given the s2k's less than ideal rear view.
Problems of install - sensors not all pointing even (2 in number plate section point slightly up an 2 on bumper slightly down) so the unit accuracy is not perfect though adequate - I had to solder splice the connections - fitting the readout display unit I had to glue to dash.

All in all my parking is way more consistent and slightly less physical :-)

 

Cool! Can you post some pictures for us?