Yesterday the rogue in my campaign was grappled by a Kelubar demodand, and tried to break free with no success. Understanding the demodand was a tough wrestler, he decided to use his ring of blinking to "blink" out of grapple. I made him do it, but I was wondering how one should have played strictly by the rules. Can someone use worn items when grappling?
You can certainly activate the ring while grappled (command word activation, standard action not requiring both hands to perform). See the activation requirements for various magic items to see if they would work while grappled, you'll find that almost all of them will perform in a grapple if you have them in hand/are wearing them.
The Blinking interaction with the grapple is more problematic. Nothing in the spell description mentions removing the grappled condition, but it stands to reason that an ethereal target cannot be grappled by a material grappler, even with a grapple in place before the target becomes ethereal. I believe you ruled correctly in all aspects here.
Edit: Barring those (rare) instances where the grappler can interact normally with ethereal creatures.
You can certainly activate the ring while grappled (command word activation, standard action not requiring both hands to perform). See the activation requirements for various magic items to see if they would work while grappled, you'll find that almost all of them will perform in a grapple if you have them in hand/are wearing them).
The Blinking interaction with the grapple is more problematic. Nothing in the spell description mentions removing the grappled condition, but it stands to reason that an ethereal target cannot be grappled by a material grappler, even with a grapple in place before the target becomes ethereal. I believe you ruled correctly in all aspects here.
Actually, it is a little more complicated than that. Blinking will only free you from a grapple if the grappler cant not effect things on the ethereal.
For example, if you were grappled by a monk with an amulet of might fist that granted the ghost touch ability, then you would still be grappled. The monk could not see you when you blinked to the ethereal, but he could still hold on to you.
Fun idea Charender!
Any DMs worried about this, just make sure to tell players that get rings of blinking that the activation is done by rubbing the ring with the other hand - no command word needed! Thus grappled it would be a forbidden two-handed action.
Of course that ruins all the silenced, locked room traps...