I think that it depends on you.
How serious are you about racing. Serious enough to spend the money on the telemetry and then actually use it to keep track of how you run under different conditions? Or would it just be a novelty? Do you like to have stuff just becauseit's cool o have?
Or would the money be better spent on different suspension parts or track time to practice driving?
Personally, I think that it's mostly esoteric BS that will probably only benifit a very serious racer.
Will it help you win races? I doubt it. Driving skills are far more important than a bit of technology.
Would it be cool to see laps times, etc? Probably, nifty toys are usually pretty cool.

The choice is yours.