David is right about the security aspect. Essentially with Hamachi you create a secure connection to you computer just like you would if you used Ethernet to network your computers together. You would then share a folder on your computer the other user could map that share to their computer and attach the TMG database to their copy of TMG. Yes a person could hack into your computer if you left it open and unsecure.
So if I understand what you are looking for I would be more likely to use
http://www.phpgedview.net/ to do your exchange with multiple people.
Yes you would have to copy the data into your TMG database but it would be more secure, easier to use with multiple users.
I have used phpGedView before and I liked it. It was many generations ago and I am thinking about trying it again. Mainly because I could incorporate it into my current website. Secondsite is good if you only want to share your data and not let them make any changes to it.
