Redmine

I'm trying to do the same thing, and I'm not exactly sure either. I know that you would somehow need to configure your firewall/end security devices if you have them to allow the connection if that even applies, and you would somwehow need to have your redmine use an external address, or something similar so that anyone could get to it, but then you would have to think about security, and who you would want to see what. Maybe a proxy login to the internal redmine might work, or if you don't use LDAP for authentication just setting it up to be accessed externally might be enough. You can configure users so that non-members can't see anything.

I got it working finally. The problem here was that i didn't have access to the firewall and the person helping me with opening the right ports told me he opened one port but instead he opened another. Stupid error, i know.

What you can do is run Redmine from port 443 and use self signed certificates in order to have a fairly safe connection.

Good luck!