Yes it was done 10 or 12 years ago. A company marketed a system that had a parachute packed in a box mounted on top of the plane. I'm not sure I remember how it was deployed; I don't think it was a rocket but more like a spring that would kick the parachute out. It would activate when the pilot released a spring loaded switch. I remember the video showed a trainer in a power dive and the parachute popped out and floated it to the ground.

It's been discussed here before, but I'm sure the company is long since gone. Because of the reasons everyone has listed above; takes time to deploy, too expensive, too heavy, etc. Just not really practical.

Now what I'm waiting for is a transmitter with a 'pause' button![8D]