+1 good idea.
I know that the *other* gc site has similar icons: .
Although I think, that particular icon is more "Are pets allowed" rather than "Is this cache feasible with a dog." I think the later would be really helpful as the last cache I did with my dog (the second of two, I'm new at this ) the undergrowth/bramble was so think I had to pick him up and cary him to the cache. Twas ok 'cause he is just a pup, but when he gets bigger...
So yes, +1 good idea.