Only selling tshirts, decals, stickers, and other cheap goodies for my Sneaker Community. What online store out there is good not only on the computer but also mobile friendly?

Mobile Compatible for the view and the admin would be great, but either/or is fine. If i can easily add a product through my iPhone would be phenomenal.

I know i can easily just create a page and add a paypal button, but i would like to keep track of my inventory, provide discounted coupons, etc.