that would take a message from a source and redistribute it to any number of other messagig systems (SMS, twitter, etc.)
This part of your idea is great. But I think by thinking of it as a distribution method for offers/discount/publicity is just meh...
Think of application of this idea in areas such as pinging someone on different channels or someone getting a choice of what media they want to receive alert on about something important (not just another crappy promotional offer).
If you are a system administrator, you most probably know there are much more important alerts/messages people willing to send/receive than a 10% discount coupon or PR shrill.