Maybe. If the application makes the D-Bus method call itself, we can get its PID (via org.freedesktop.DBus.GetConnectionUnixProcessID) and use that to identify the caller. If the application invokes dbus-send (or similar) to make the method call, we're out of luck.

In any event, it'd be a nontrivial undertaking to develop this feature and extend the configuration file format to accommodate this. I probably won't do it myself, though patches to implement this (or any other) feature are welcome.

(As an aside, my day-to-day device these days is a Nexus S running Android. I'll continue to provide bugfix support for Browser Switchboard, but if someone is willing to take maintainership and push new features in, I'd be willing to consider the offer.)