This is a guide to enable SMS for the Google Nexus 7 tablet.
http://forum.xda-developers.com/showthread.php?t=2535586 (KTU84P SMS WiFi Tether under downloads)
http://www.wugfresh.com/nrt/ (NRT_v1.8.8.sfx.exe under downloads)
Download all files in the Downloads section
Update your Nexus 7 to Android version 4.4.4 build number KTU84P (checked under Settings -> About tablet)
Install the USB drivers following these directions: http://developer.android.com/tools/extras/oem-usb.html#InstallingDriver
Run the Nexus Root Toolkit and allow it to update all binaries
Pick Nexus 7 Android 4.4.4 KTU84P for model type
Press the Unlock button in NRT and follow its directions
Select the Custom Recovery checkbox under Root and press Root button and follow its directions
Select Launch under Advanced Utilities
Select "File is on this computer" under "Flash Zips"
Select "Flash Zip"
Press "Add Zips to Flash"
Select the zip you downloaded previously
Select "Confirm Operation" and follow its directions
Continue setting up as described in Android Phone Setup