I do carry turbo timers and as said before they all perform the same function. As you can see the APEX-I does have other features that some might like to have, for most they are unnecessary though depending on what other instruments you are running in your car. I would suggest using any of the following for your setup:
-HKS
Type-0 is a basic turbo timer that basically does it's job, nothing more nothing less.
Type-1, the Type-1 offers you the ability to see your RPM's and Vehicle speed within the display, again I feel this may be unnecessary for some applications.
-Apex-i
The Auto-Timer is a nice, small design. It does the typical function of a timer and also boats it can read theoretical air/fuel ratio through the o2 sensor. I don't know that I would depend on this reading.
-Blitz
*FATT DC features a built in lap timer, in-car temperature display and battery voltage. The lap timer is a nice feature.
*DUAL CC includes the same features as the FATT DC (excepting battery voltage and in-car temp display) plus a boost pressure display, peak boost, and over boost warning.
-Greddy
*Full Auto Timer offers the standard features of a timer as well as a stopwatch/lap time and attack modes along with a built in voltmeter and speedometer.