This mod can be flashed via TWRP or CWM recoveries on odexed and deodexed stock based ROM's and will enable SMS options in Settings. By default SMS will appear in Hangouts as per the Nexus 5.
Revert is only for stock odexed users. Should you need to restore a deodexed ROM simply reflash it.
LRX22G SMS (5.0.2)
LRX22G Revert to stock (5.0.2)
KTU84L SMS (4.4.3)
KTU84L Revert to stock (4.4.3)
KOT49H SMS (4.4.2)
KOT49H Revert to stock (4.4.2)
KRT16S SMS (4.4)
KRT16S Revert to stock (4.4)
If you have a 2012 Nexus 7 get the mod here
@fisha21 for putting up with my constant ranting about Google removing SMS and helping out.