The other end of the VPN is sorted 60 quid a year and there are about 20 world wide servers and the openvpn client is pretty robust in my experience and if one route fails will quite happily go looking for another server.
The box is just that with an Ethernet port, a webserver to do the setup on it, a speaker, microphone and I presume a DEC interface to the triggers. I have a sneaky feeling it does actually use VoIP for when its triggered and is pretty easy for the ISP to sniff that and block it. So the proxy option is out.
Once I have the guts of it sorted out its not actually very complicated. I will have basically created a VPN router, a couple of cron jobs to do the house keeping and restart the VPN connection every 24hours so we don't get any security certificate errors. Barring hardware failure it should be pretty robust, its not as if the coffin dodger is going to be using the laptop.
You don't need install any routing software on unix boxes to route its all under /proc/sys/net/ipv4/