http://hg.tangent.org/skeleton-mysql-engine
This week I gave a presentation at the PHP Vancouver conference. I showed off how to write a pluggable I_S (wrote it the span of about two hours). You can get the code from here:
http://download.tangent.org/vmstat_information_schema-0.1.tar.gz
The presentation can be found here:
http://krow.net/talks/PluggageInformationSchemaVancouver2007.pdf
Finally there is inside of the 5.1 tree an example of a daemon plugin in the plugin/ directory. It just shows how to generate a thread and creates a simple heartbeat file. If I get a chance I'll add an example of how to have it also generate a network heartbeat as well (should be einfach).
BTW I've released the latest version of the memcache engine for MySQL. You can find it here:
http://tangent.org/index.pl?lastnode_id=478&node_id=506