PSIA is a competing open standard for Network Video devices.
PSIA stands for Physical Security Interoperability Alliance
PSIA looks like the people who weren't invited to the ONVIF party looked at their specs, and went hmm, then implemented something better.
PSIA uses REST instead of SOAP, so its a lot smaller sizewise for implementing from a client perspective.
No SOAP XML verboseness for a start!
PSIA site is here - http://www.psialliance.org
Unfortunately they're less open than ONVIF with their documents, so nothing freely available for the moment.