This app does not only require root, it requires specifically SuperSU version 2.40 or newer, due to how the boot-time code is launched. Alternatively, the app will try to function for otherwise rooted firmwares that support init.d, but this is not officially supported and it cannot be guaranteed to work.
LiveBoot is a boot animation that shows you logcat and dmesg outputs on-screen as they happen. Output configuration includes logcat level, buffer and format selection; whether to show dmesg; the amount of lines that should fit on your screen, whether word-wrap should be employed, and if output should be color-coded. Additionally the background can be set to transparent to overlay the existing boot animation, which looks awesome during boot.
A feature is built-in to test your current configuration without rebooting. The lines shown in test mode may be limited and relatively static, this does not reflect exact boot time behavior as much as it just shows you that it works and how big the text will be.
Note that LiveBoot will only show up after the data partition is mounted. If you need to enter a decryption key or pattern at boot, it will not show up until you have done so.
Editors is lazy not tested it