Nope, I just use the AC adapter or USB cable to charge my devices. The powermat might be good for people who need to charge their batteries a lot or if they have a limited number of power outlets, but a lot of things to charge.
They might be good if the charging port/plug and AC adapter breaks, and you can't charge with the regular charger because the cord or charging plug on the device breaks.
Another up side to this is if you lost your AC adapter since this mat is a lot harder to lose since it is so big.
I think most people just buy this because it looks cool, or to save a few seconds of time looking for chargers.
according to the video. This mat charging device uses Magnetic Induction.
This video kind of explains the basics of Magnetic induction. From what I understand from the video, the metal does not have to make contact with each other to charge something.
You have to buy a powermat receiver designed for the Nintendo DSi like this one http://www.amazon.com/gp/product/B002NUIAWU?ie=UTF8&tag=johsgamsto-20&linkCode=xm2&camp=1789&creativeASIN=B002NUIAWU
