Kawada sells a servo saver that has a sheer pin in it. The idea is that it acts as a solid arm, but if you hit something, the pin sheers off, and you get the benefits of a servo saver. I think it's a fine idea. Unfortunately, I find the pins are ridiculously fragile. Any... ANY incident will make them snap.
The servo saver (it's the kind with two circular rings as springs, like a Tamiya) is really nice though, even without the pins in it. It's a lot less sloppy than the Kimbrough.
Kawada B29S (Direct Servo Saver w/Lock)
Kawada B29X (Shear-Pin for Servo Saver)