intercepting WAL writes

Hello,

I'm new to the core PostgreSQL code, so pardon the question if the answer is
really obvious, and I'm just missing it, but I've got a relatively large web
application that uses PostgreSQL as a back-end database, and we're heavily
using memcached to cache frequently accessed data.

I'm looking at modifying PostgreSQL (in some way) to push changes directly
to our memcache servers, in hopes of moving towards a system where only
writes are actually sent to the databases, and reads are exclusively sent to
the memcache servers.

I'm guessing that I could intercept the WAL writes, and use this information
to push out to my memcache servers, similar to a replication model.

Can somebody point to the most logical place in the code to intercept the
WAL writes? (just a rough direction would be enough)- or if this doesn't
make sense at all, another suggestion on where to get the data? (I'm trying
to avoid doing it using triggers).

Thanks,

Mike