OpenBSD does some of that; obviously, OpenBSD doesn't do the "Linux
Virtual Server" stuff. CARP does allow (nearly) transparent fail-over of
routers, and relayd and lots of ports can handle fail-over of backend
servers.
I have no experience with or opinion on keepalived. You may get more
useful answers if you ask more specific questions, preferably on
mi...@openbsd.org. Do make sure you've done your homework first.
Joachim