In 6.2(1) you can do LAN-based failover, but it'll only span between sites if you have an ethernet subnet between your sites. The feature was built to overcome the 6 feet length limitation of the serial cable - I think it'll be put to use mostly by people who place their machines on opposite sides of the same datacenter.
You can read up on:
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_62/config/failover.htm#xtocid4
In step 13 you'll see the commands that are specifically related to LAN based failover.
Good luck.
Frans
