Hill Climb Timing System

I am building a routed hill climb (see Brenner Pass Hill Climb thread) and need to find a timing system. I would like to set it up so that there are three sensors (provide an intermediate and finish time, as well as be able to get a lap time - bottom to top and back down)

I would need one sensor at the bottom for the start, an intermediate sensor half way up and a sensor for the finish at the top of the run. Any suggestions on what I should get and where? I have checked out the Carlson system but he seems to be on sabbatical. Any other ideas? I am prepared to install in the track and have routed "holes".

I gather that I can program Ultimate Racer 3.0 to run as a hill climb. Any input here?