IMHO you should keep the Interceptor. You listed several parameters that I monitor on my trucks constantly. The ability to view the IAT1, IAT2, voltage, tranny temp and coolant temp parameters constantly is very convenient and will help you identify issues before you find yourself in need of a tow.
I bought the Interceptor for my Lightning shortly after they hit the market, unfortunately that was over a year after my IC pump crapped out on the I-8 interstate while towing my ex-wife's car from San Diego to San Antonio.
I did have an Interceptor in my old Power Stroke to alert me to the fact that my alternator failed on me, also while drive between San Diego and San Antonio on the I-8 freeway. The Interceptor is a good piece of mind.
I also appreciated the Interceptor in my HD when I moved back to San Diego and had to climb the mountains pulling my Lightning. The Interceptor allowed me to watch my tranny temps and keep them in check. I know a handheld can monitor these parameters but I personally don't want a hand held tuning device constantly propped up in the center console or sitting on the seat.