I might be interested in buying one. Will it work on a Samsung Galaxy S5?
Hi there! The controller works with any Android device with BT Keyboard capability. I've used it on the Nexus 7 with an aftermarket ROM (Cyanogen) on there as well as a Motorola X with the stock ROM. As the S5 is newer than the two devices I've listed, it should work just fine.
Bonus - if the S5 has USB host capability, you can pick up a USB OTG cable and use the controller that way as well