I currently use a Synology NAS which has a similar feature, although it's not a data replication process, but a scheduled backup. I use a 1.5TB external USB HDD every once in awhile to back things up, then drop it off at my parents house in case of fire. Synology offers something similar to what you are looking for, although it's data replication between Synology servers and not an eSATA drive. Some models offer eSATA ports along with the USB ports and gigabit Ethernet ports.
Any objection to firing the backup manually before you move it off site? If not, then you might want to take a look at their products. They are well built and the DSM software is second to none. It has a ton of features that most people rarely use, such as a built in webserver, FTP server, Audio Station, Photo Station, Time Machine Server, iTunes Server, and the list goes on and on. Here is the FAQ
on the built in backup utility.
This is a link to their website
if you are interested in checking out their products.
Edited by Spyderturbo007, 15 April 2011 - 06:46 AM.