Exchange 2010 includes a feature called Datacenter Activation Coordination (DAC) mode that is designed to prevent split brain at the database level during switchback procedures that are being performed after a datacenter switchover has occurred. One of the side benefits of enabling DAC mode is that it enables you to use the built-in recovery cmdlets to perform the datacenter switchover and switchback.

You can download it from here
Note: It's not exactly a tool but a power point guide to help you perform the switchover correctly with all the cmdlets.

Cheers,