Tethering isn't detectable. No matter what device is using it, it still just shows up as data use. I have tethered a PC, my iPad, and a Kindel in the same hour. Checked my data use online, and all it showed was Data. People get caught or questioned when all the sudden their data use sky rockets.
Sent from my iPad using SatelliteGuys
Are you talking AT&T? I never used more than 2-3 GB/month. I tethered for a couple of days for an "emerency" situation. About 10 days later, I got a text from AT&T that stated I would be removed from the unlimted plan if they detected unauthorized tethering again. It wasn't the spike in usage, it was simply the fact that I had tethered.