Over three years ago when I purchased my Surf Shelf it was over $50. Since then it has gone up in popularity and come down in price ($40). The clear poly-carbonate shelf is just as durable as when I bought it. If you want a simple solution for working on your laptop while exercising then I highly recommend checking it out. I find it easy to get caught up on my email, social networking, and other reading while walking. At a quicker pace it is nice to have the TED videos accessible in full size instead of trying to watch them on my iPod.
The basic mechanics: the shelf has super long click buckles that secure the shelf to the trendmill and then another strap to secure your laptop to the shelf. It does not budge. If you make the rounds at the gym this unit is easy to unhook and transport to a new machine. Here is a quick video from the makers of this exercise accessory showing how easy it is to attach and use:
The Surf Shelf works for many different exercise machines and not only trendmills. The official SurfShelf website states their shelf fits 99% of trendmills as well as elliptical trainers and other stationary equipment.
The only downside I have found is that on some machines, if you have a big laptop (mine is 17″) it makes it difficult to read the exercise display screen depending on where it is located to see how far along you are in current program — if you are not obsessed with seeing the lights indicators go up and down etc. in your current activity then it will not be much of a hindrance.