First introduced during CES 2015, the AT&T Modio case will be available starting March 20 for all three versions of the iPad mini. The case acts as an LTE hotspot for your iPad, and is available either at its full price or on a plan, according to AT&T:

Connect your iPad mini with Wi-Fi to AT&T's 4G LTE network and protect your tablet at the same time. The Modio case can be purchased for $49.99 with a two-year commitment, roughly the same price you would pay for a case just to protect your iPad mini. It's also available on an AT&T Tablet Installment plan for $10 per month for 20 months, or at no annual commitment for $199.99. Add the case to a new or existing Mobile Share Value® plan for a $10 per month access charge.

The case comes with a 4,600mAh battery for up to 16 hours of continuous use. Additionally, the case contains a microSD card slot, allowing you to add up to 32GB of storage space for documents, movies, and more, accessible on your iPad using AT&T's Modio Data app. A version of the Modio for the iPad Air and iPad Air 2 will be available later in 2015.

Source: AT&T