This app only works on Nexus 7 (2012 & 2013), Nexus 4, Nexus 5, OnePlus One, Sony Xperia Z (yuga), Motorola Moto G (1st gen) and HTC One M7 and M8 and Samsung Galaxy S4 (i9505).
This application requires root and it is designed to be used by experienced "power users". It is strongly recommended to read XDA thread before installing this app, you can find links at the bottom of this description.
MultiROM Manager can install or update MultiROM, it's recovery and kernels. It can also install Ubuntu Touch system-image based builds into MultiROM as a secondary ROM.
MultiROM is one-of-a-kind multi-boot mod for Android devices. It can boot any Android ROM as well as other systems like Ubuntu Touch. Besides booting from device's internal memory, MultiROM can boot from USB drive connected to the device via OTG cable. The main part of MultiROM is a boot manager, which appears every time your device starts and lets you choose ROM to boot. You can see how it looks on the left image below and in gallery. ROMs are installed and managed via modified TWRP recovery. You can use standard ZIP files to install secondary Android ROMs, daily prebuilt image files to install Ubuntu Touch and MultiROM even has its own installer system, which can be used to ship other Linux-based systems.
See XDA threads for more information:
Nexus 7 (2012): http://forum.xda-developers.com/showthread.php?t=2011403
Nexus 7 (2013): http://forum.xda-developers.com/showthread.php?t=2457063
Nexus 4: http://forum.xda-developers.com/showthread.php?t=2472295
Nexus 5: http://forum.xda-developers.com/showthread.php?t=2571011
OnePlus One (unofficial): http://forum.xda-developers.com/oneplus-one/development/mod-multirom-v26-t2835738
Sony Xperia Z (unofficial): http://forum.xda-developers.com/xperia-z/orig-development/mod-multirom-v27-t2843976
Motorola Moto G (unofficial): http://forum.xda-developers.com/moto-g/development/mod-multirom-v27-testing-t2852897
HTC One M7 (unofficial): http://forum.xda-developers.com/htc-one/orig-development/mod-multirom-v28-redesigned-gui-t2880887
HTC One M8 (unofficial): http://forum.xda-developers.com/htc-one-m8/development/multirom-v28-unofficial-port-t2884413
Samsung Galaxy S4 i9505 (unofficial): http://forum.xda-developers.com/galaxy-s4/i9505-orig-develop/mod-multirom-v28-t2864469
Donate version: http://bit.ly/1nSnu2o
PayPal donations: http://bit.ly/mromdonations
Source code: https://github.com/Tasssadar/MultiROMMgr