Ever since phone and tablet makers have started including powered USB OTG (Ability to plug in full size USB devices into a phone or tablet). The main use so far has been plugging in flash drives, card readers, keyboards, mice, and game controllers. The issue with this setup for flash drives/card readers was that it was rather bulky.
The Meenova project was released on the crowd funding site KickStarter with the goals of selling a compact OTG centric micro SD/SDHC/SDXC card reader back in early 2013. One key part of the product was the inclusion of the adapter to use it on your desktop or laptop computer and the ability to carry it on your keyring. Provided you use a fast enough MicroSD/HC/XC card (eg. clas 10) you will get some pretty fast transfer speeds.
Of course having a Android phone is not enough for this to work your phone needs to be on the supported device list. The common supported devices are most Samsung, HTC, Motorola, Nexus (except Nexus 4), and many other devices. Also on some devices you may need to use 3rd party software such as Nexus Media Importer, StickMount or OTG Disk Explorer (Last two requiring your device being rooted).
Over all I’d say Meenova is well worth it if you heavily use your phone or tablet and got limited storage due to no expansion card support or want to have additional storage. It is a real bonus for owners of rooted devices since you can backup/restore your device in addition to install roms from it.
If you are interested check it out at their site http://www.meenova.com.