Some forum posts I have read on TMobile, speculate that using the WiFi Hotspot feature alerts your provider by browser agent info, and that tethering an Android, iPod touch etc will not be detected, therefore the added cost for the plan will not be added to your plan. I don't know how Verizon handles the HotSpot feature, on TMobile it is enabled by default, and so far I have not seen any charge added to my phone bill.