BootNow is a separate free product (available on the BootIt BM download page) which allows you to select a boot item configured in BootIt BM (or BootIt NG) from within supported operating systems. BootNow works with most versions of Windows, including Windows 9x, ME, NT, 2000, XP, Vista, and Windows 7/8.x/10. BootNow is also available for Linux, FreeBSD, Solaris, and eCS - OS/2. A DOS version is included in the Windows version download.
From the running OS, running a configured BootNow item (e.g. in Windows, double-clicking the BootNow shortcut icon) will shut down and restart the system with the selection you chose. For example, you might boot to another installed OS or run a script and boot back to the current OS.
BootNow also has an option to run idle in the system tray waiting for the system to hibernate. When the system hibernates, it will automatically set up BootIt to boot the prior booted boot item so that any hibernated OS is resumed without the option of booting a different OS. This is desirable when partitions are visible across different OSes and you use hibernation. It prevents changes to the partitions the hibernated OS has access to, as recommended by Microsoft.