We don't always want to follow along with a video but every now and again it would be handy to have the video set up so you can remind yourself how your supposed to get into an asana or how to exit. Synch your video with your itouch and you can jump to the appropriate section without leaving your mat. Likewise with a bit of nifty editing you can add a photo album of a series and scroll through to the asana you want to check up on.
I took a photo of Matthew Sweeney's 3rd Series and downloaded it to iphoto. From there it was just a case of duplicating the photo 30 odd times and cropping each picture down to the individual asana. Turn it into an album and synch it with your itouch and away you go.