Cardstick Decal

Available in sets of 3 for just $3.99, you get a clear, white and yellow vinyl sticker that features inch markings on one side, and centimeters on the other. The decals are also thin enough to not block the card's magnetic strip, which really shouldn't be an issue though. You can also slap the stickers on just about any surface, like the back of your phone or the lid of your laptop.

Source: ohgizmo.comAdded: 8 September 2011