Available in 8 colors, Grantwood Technology's Tuneband ($20) is a combination of a silicone rubber iPod nano case with a Velcro and fabric armband and a "cut it yourself" film screen protector. The case leaves the nano's bottom open for connection of the Nike + iPod Sport Kit and headphones, and the screen protector sheet has line drawings of the second- and third-generation nanos to help you snip out whatever film coverage you think you need. Tuneband…