Have just come across what could be an AlertMe alternative...
http://www.responseelectronics.com/burg ... iguard-c36
It's launching under the MiGuard brand in the UK very soon and is created by a company called Chuango Security (Response are UK distributor).
There's a lot more information and additional accessories featured on the Chuango website...
http://www.chuango.com/english/