Price: £39.99 (plus £4.99 p&p) Sensors/alerts: Four/audible & display

At less than £45 all-in, the NIK4R is the cheapest package here, yet still includes four sensors. A small pictogram of a car simply flashed in time with the beeps, so it’s probably not worth the effort to run the long cable from front to rear. Still, performance was impressive, particularly on the hose reel, which was accurately maintained from 80cm.