Though Leopard Flower matches what you described, I'm not sure it is the best solution out there. It was just the first I found
Currently it looks like it is only available as a source package, so you will have to compile it (sounds scarier that it is). The Linux Mint developers are but a small team, and I think they have enough to do without also becoming package maintainers for various applications. So I'm not optimistic about this idea getting implemented. But perhaps I'm seeing this wrong
It would perhaps be a better idea to ask the application's developers to build Debian packages or create a PPA for it on Launchpad (a build service that builds applications from source and makes them available to Ubuntu users, which includes Linux Mint users).
Ideas for software inclusion you can submit as an idea on the community website: http://community.linuxmint.com/
. Though be ready for the reply "Linux is not Windows", as the need for an outbound firewall on Windows developed from all the spyware and other malware that is so prevalent on Windows, where you basically can't trust your own computer (exaggerating, but you get my drift). Though it would be silly to say such threats are not present on Linux, it is nowhere near as big an issue. Hence many users only need a strong inbound firewall to protect them from remote attackers (as they only install software from signed and trusted sources the risk of having spyware or other malware on their computer is almost non-existent).