This may sound stupid but, if you dont mind about the speed aspect of things and are only worried about not being able to receive emails etc if your adsl connection goes *** up, then zen does have a backup system where you can use a dialup modem to access the internet, now their is less chance of that messing up like adsl as its your physical phone line, so unless your actual phone line died and you cant make any calls at all, then the dialup modem will always connect regardless if your adsl line is working or not.
That would also save you money as all you would need to buy is a 56k modem and just have it setup to use when your adsl goes titsup.
Ok, the obvious bad link here is the speed, but as I say, if your not really worried about speed and are only needing the redundancy to access emails and alike then its worth looking into, unless as cyteck points out, if your a big business or a medium sized business or even just a wealthy broadband user then obviously you wouldnt wanna be stuck with 56k speeds if you have the cash to spare to get a decent second line.
I also doubt that Sat internet is the answer, I know a couple of people in the states who have it due to them living miles away from any exchange for cable or dsl, so they opted for Sat and both of them have not been happy at all with the service they are getting, maybe they are expecting too much from said service, but they are definetly not happy with it and both are waiting for their contracts to run out so that they can go elswhere if possible.