Default Wireless Button to Activate Google Voice Search

Anyone have any unique ideas on using a wireless button to activate Google voice search or some other task on Nexus 7. I am able to do this using my Bluetooth headset on my Nexus 5 by hitting the call button. Unfortunately the Nexus 7 does not recognize the call button when I pair the same headset with the Nexus 7. Any ideas or accessories that could do this?