Transmission Temperature gauge kit for 07 Silverado?

[victorb]

I am sure this question has been covered but I can't seem to find an answer using the search on here. So if it is posted somewhere else, just point me to it please.

I have a 2007 Silverado 1500 LT. I want a transmission temperature gauge for it. I have been looking around at the option and I am unsure about what to go with. It appears there are three options. Option 1: Gauge with sending unit that installs in the trans oil line. Option 2: Gauge with sending unit that installs in a port in the tranny itself (if available). Option 3: An OBD2 plug that send the temp to an Android smartphone via bluetooth.

So here are my questions.

Question 1: Of the three options, which is the best?
Question 2: Does the transmission on my truck (4L60E) have a port that can be used for option 2, and if does; what is a good kit to be used with this option?
Question 3: Does the transmission really already have an internal temperature sensor that can be accessed via the OBD2 option and how reliable is this method?
Question 4: If option 2 and 3, are not available or reliable, what is the best kit for option 1?

Thanks guys.