Where to buy a 2 stroke tachometer?

I bought one of the cheapies off Ebay.

It has the ability to be used on a 2 stroke engine but if you want a NICE one, trail tech makes mountable "heads up" units. Temperature, clock, head temp, tach. Nice, but pricey...
 
tachs are for 2 things ?????? shift points and rev limit ????
which are you guys using them for ????
 
i could see a tach being handy for a few different reasons, a trail tech would be my first choice but like civic said they are a bit pricey