Although everybody is advertising them as Bit Char-g lap counters, all of the ones I see advertised clearly state that they are Bit Racer lap counters, ie. they are designed for cars running on tracks. The small piece of track you can see attached to the backside indicates this as well. From the picture at tinyrctoys, I'd guess theirs is the Bit Racer type
TinyRCToys picture:
Picture of box:
It seems it would be really hard to get a car to hit that small a track opening. Maybe you can disasseble it to use just the counter part.
On the other hand, there clearly is a Tomy Bit Char-g lap counter as well:
This seems to be based on IR to count the laps. The problem then, of course, is how do you count laps for individual cars? Unless you can fit an electronic Id into each car to be read by the counter, something like this would never work when all the cars are running on the same track.
It might be OK for training though.
My advise would be to spend the money one something else.