US Bank Cash+ has a 5% cell phone cash back category (this quarter its all bill pay including cell phone). I recently bought a pre-pay SIM activation kit (for my nexus 4 to test) from the t-mobile online store that counted for the 5% category. That said, if you dont already have the card, the latest i heard was you had to visit a US Bank branch to apply.

The chase business cards give 5x for cell phone as well. dont know if the hardware counts.