The Blue Sea ACR is dual sensing. See FAQs link below:
http://bluesea.com/viewresource/1366
I am going thru this right now also. I have decided to go with the Blue Sea ACR and Dual Circuit Plus switch. Was able to buy each separately on EBay brand new for a total of $67 shipped!
Here is a link to the Blue Sea 5511E switch (the same one that comes with the add a battery package) for $16.99 (plus $10.55 shipping). I bought one plus found the ACR for $40 shipped (they only had one of the ACRs).
http://cgi.ebay.com/ebaymotors/New-B...ssoriesQ5fGear