APM support for X11

is that just tunnelling certain traffic? seems like a application tunnel should be able to work.

It's TCP and usually listens on ports between 6000 and 6063, so you may need to create a wildcard port VIP and then adjust the allowable range with a packet filter or iRule, or require a specific port. But otherwise there should be no reason why you couldn't push layer 4 X11 traffic through an LTM VIP. There is no direct layer 7 application proxy support, however, if that's what you're asking.