Here’s a neat idea: at least until all cameras have built-in Wi-Fi anyway: It’s a Wi-Fi SD card adapter — like the Eye-Fi cards, only instead of packing their own flash storage they have a hole which will happily hold a the microSD card of your choice.
Thus, you buy the adapter once, and stock up on a (small) pocketful of mini memory cards. This, the thinking goes, will be cheaper and more future proof than building Wi-Fi into every damn SD card you use.
First off, you aren’t going to want to shoot hi-def video onto one of these, at least not for extended periods. Generally, microSD cards aren’t optimized for speedy read/write performance (although this isn’t always true). Still, however slow your card is, the Wi-Fi transfer will be slower, so if all you want is to easily beam your photos from camera to phone or iPad, then you can just toss in the crappy microSD you got free with… well, everything.
A companion app does the receiving, and can be had for both iOS and Android. The card supports up to three connection simultaneously (unlike the Eye-Fi which requires reconfiguration to beam to a new device), but has no geolocation abilities (not that Eye-Fi’s geotagging works with mobile apps anyway.
Despite its glitches, I use the Eye-Fi (or at least the SanDisk-made version) every day to get photos from my camera to my iPad. The PQI Air (as it’s called) might actually be a better choice for Android users, as if everything goes wrong, your phone probably has a micrSD slot so you can just drop the card in there.
Source: Digital Photography Review.