Hmm, I guess I should clarify what I would like to see.
I was thinking of something more in line of a Spyderco yoyo, no blade in it (ouch!). It would be made of zytel and of good weight with a tough cord, and patterned like the endura grip with the spyder in the middle. Offered with an Endura, or possibly a Matriarch (if possible) both in the same color handle material.
The basic idea is that if for whatever reason, you can't have your knife you can have your yoyo, since it is regarded as a toy. If you need to use it in a defensive situation you can. If not it is a neat little toy to have around. I agree that there is a certain comedic aspect involving a defensive yoyo (can you imagine giving a police report saying "I beaned BG X upside the head with my yoyo and KOed him. I then used the cord to tie him up for you to get here, Officer sir". The look on the cop's face would be priceless) but if one were forced to, it could be pressed into use as a defensive weapon. I think we are all pretty much familiar with the yoyo's roots, regardless of what has been made of it.
Although this is not something I really expect to see offered by Spyderco, I thought it could not hurt to ask Sal for his thoughts on the matter.