Parking Sensors. Are they any good?

[mac100]

I intend to install parking sensors on my new car and am considering the Taurus T123P parking sensor which uses electro magnetic technology with an antenna mounted along the inside of the plastic bumper thus avoiding the need to drill holes therein as would be required for the more usual ultra sonic type sensors.
I would welcome comment/opinion, from anyone who is familiar with the Taurus system, as to how effective/useful they find the system to be.
In particular
1 Do you find the protection zone (which extends to only 80cms from the rear bumper) to be adequate.?
2 Will a towbar which protrudes beyond the bumper into the protection zone be a problem ?
3 The specification states that the T123P sensors will detect small & high kerbs.
When trying to park alongside a kerb in a tight situation is a warning signal from the kerb going to be picked up which could mask a danger signal coming from the rear.? In such a scenario a driver might perceive the signal as coming from the kerb and continue backing until he strikes the obstacle behind him!

I have absolutely no experience with parking sensors of any kind and would be very grateful for any enlightenment offered

Thank you