Temperature Sensor with I2C i/f for measuring temperature at different location on the surface case and heatsink

Dear Shai - 

for the requirements you listed, the following EVM may be of interest: 

1 local, 8 remote with the accuracy needed, with four possible I2C addresses, 

http://www.ti.com/tool/tmp468qfnevm

https://www.ti.com/lit/ds/symlink/tmp468.pdf

Dear Shai - 

Please see: 

Note 5 on page 34 has some instruction about less than 8" and greater than 8" lengths for the remotes, as well as a tip on handling shielding on the one end. 

Note 4 discusses max capacitance on the D+ and D- lines, which can be measured, Figure 9 on page 9 shows why. If coax is used, usually this is about 20pF per foot, and this can be measured as well, with LCR meter or network analyzer.