KeyCloak supports revocation by means of posting the 'session_state' variable (received alongside with the response of the access_token) in the endpoint:

https://server/realms/application/tokens/logout?session_state=<SESSION>

iOS lib should support (possible by the introduction of a new keycloak specific oauth adapter)

Keycloak ML discussion:
http://lists.jboss.org/pipermail/keycloak-dev/2014-June/001940.html