iMessage across apple devices

OK Currently I have iMessage happily synced across my mac, ipad and touch.

These are all wifi devices, and I can handle that. It's bringing the iphone into the equation where I have a question or two.

My question is, is there any sync possible from say the mac but to use my iPhone text allowance, i.e. if I send a message to my Dad who still has a "feature phone" from my mac, would this be able to send from the iphone phone number if they are all linked?

Or is this linking purely inbound, i.e. if my Dad texts me, I can see the notification on the mac (for example).

One of the last sticking points for me to switch from my SG2 is texts - I've got SwiftKey which compensates for my poor text entry on a phone screen!