My iPhone 4S has a shiny, slippery back. I worry about it sliding around my desk, especially when it vibrates as phone calls, emails, text messages and other alert notifications arrive throughout the day and night. I’ve considered those special-purpose “sticky pads” you can buy at stores like Best Buy and Target. Although they would certainly would do the job, they’re way overpriced for such a simple task.
An easy DIY alternative is to use padded shelf liner. It’s inexpensive, available in different colors and can be cut to any size you’d like. I use several custom-cut rectangles as charging areas and resting places for my iPhone, iPod, GPS watch, etc. The cushioned, non-slip material is perfect.