I bought a pair of UE Mini Booms today. After much trial and error, I have now had success using them in 2x "doubled up" mode on all my devices - both my iPhone 4S & iPad 3 with this app, as well as my iPod Nano and my Windows 8 PC without the app.
At first I could not figure out how see them in the app, so I could double them up. The directions provided did not work, as far as I could tell. I could tell from reviews that some people had success, but others were complaining the app was broken. I found that I first had to connect to them individually in iPhones Bluetooth Settings. Then I had to relaunch the UE app before I was in business and could double them up just fine. The directions I read made it sound like you could find them and connect directly thru the app without having to go into the devices Bluetooth settings, but this was not true for me.
Although sound drops out in "stereo" mode, it is fine in "double" mode. However Im not sure whether this is an issue of the app, or rather specific to the device design itself??? (When doubling up without the app, it defaults to non-stereo "double" mode).
I do think there are several reviewers that are trying to pair the wrong model of UE speakers. This app requires that BOTH speakers be "mini boom". It wont work if one (or both) are not the "mini" version.