There's nothing worse than rebooting to change OS, walking off while the shutdown and POST is in progress, and coming back just as you boot right back into the environment you just left.
You can solve that with grub-reboot, but wouldn't it be cooler to select your next OS right from the restart menu?
Restart into Other is a simple tool that prompts you to select one of your grub2 menu entries. It will then select that menu entry using grub-reboot and restart.
Edit /etc/default/grub
Make sure GRUB_DEFAULT is set to saved:
GRUB_DEFAULT=saved
If you had to change it, run update-grub
$ sudo update-grub
Configure the default on all non-preselected boots:
$ sudo grub-set-default <whatever GRUB_DEFAULT was>
Install the shell scripts and put the .desktop file into /usr/share/indicators/session/applications
$ sudo make install