This accessory comes with me wherever my camera goes. The LensPen is a great utility to help keep your camera lenses clean. The LensPen is a double-sided cleaning tool in the shape of a pen. One side contains an extractable brush for dusting away particulate matter collecting on the lens. The other end of the LensPen contains a cleaning tip that contains a chemical cleaning solution which is released when it is rubbed against the lens surface. It also has a clip like any other pen so you can clip it to your shirt if you want to. I tend to just keep mine in my pocket. Its compactness makes it a great tool.
I've had my LensPen since I got my first SLR camera. While the cleaning solution has long since been used up, the cleaning tip still works great to remove smudges from the lens surface. LensPen claims to be safe for all lens and their coatings, and as I've never had any issues, I can confirm that for at least my Canon lenses.