Debi: I'm happy with the ability as is, thank you for the suggestions. As for your last comment, are you under the impression that a creature has to use every single attack listed under full attack when performing a full attack action? If I used the word "or" that would signify one or the other, not one or the other or both at once. What would be most accurate (as "or" is in fact not accurate in the slightest) would be "and/or" but since creatures can simply chose not to use an attack if they want to, in D&D this is simplified to "and". A full attack is simply what happens when you use more than one attack.
I was going to say that the penalty would be reduced by 5, as you suggested, but I found it much simpler to allow them to use a tentacle attack as a swift action (they have nothing else to use on swift actions anyways) so as to further the idea of the tentacles being autonomic. My ability effectively has the same result, just with different methods. That is regarding standard action attacks, at least. I clearly state that with a full attack they do not receive any penalties for it being a secondary attack.
Alas, I do not know the d20 Modern system, although I agree it would fit nicely. Thank you!