Ah good idea, how would I go about crimping the 3 wires together though? I assume I would have to snip the reverse power wire, bare the two ends, crimp them and crimp the power wire for the sensor box, whats the best way of connecting them all afterwards?
Or could I snip the reverse power wire and crimp them into the 1 connector?
If you get a decent bag/box of assorted crimp connectors you should find that there's a 3-way connector type in there. Can get them pretty cheap from Maplin with a crimping tool included.
So yeah, you'd have to snip the reverse wire and then crimp both ends into the 3-way connector along with the live wire for the sensor.
But if you can't get a 3 way connector then just shove two wires into one side of a normal two-way connector and the other wire into the other side.
Doesn't really matter as long as they're all securely connected.