WOW mark you are so helpful
I have been looking for a lap counter for quite some time and they are hard to catch.. Team Orion dont make them anymore and all the others seem to be too big.. Spektrum seem to be doing somthing but still not seen anything other than the Sensor part.
To be honest i have found it better to have your team mate watching and timing... least then you got someone who can give help.
iPhone has a laptimer built in and once you get the hand of hitting the button at the right time its good enough.. I am sure most mobile phones can doo the same.
Hope this helps