Sounds like an excellent idea
If the offering is "up to", the the bill should also be "up to".
Say you are paying £24/month for a connection that is "up to 24Mbit". So you have an SLA checker device (it'd have to be a black box appliance provided by a 3rd party" that checks the sync speed of the modem and the bandwidth to one of the designated test servers several times/day at random intervals (random to keep it fair and unpredictable to precent abuse). The test servers and the appliances would have to both be run by an independent 3rd party to ensure veriviability of the results and prevent abuse by users and ISPs.
For every 1 Mbit average on the tests during the month below the "up to" advertised figure (if there is no connectivity, e.g. modem (usually owned by the ISP and thus their responsibility to fix/replace) or exchange fault) that check counts as 0 Mbit/s), you would expect to pay proportionally (in this example £1) less per month.
Inherently fair and very workable. Now we just need an independent 3rd party to provide the monitoring appliances and the testing infrastructure. Of course, this 3rd party would have to be funded, e.g. by an additional monthly subscription + purchase of the tester appliances which those interested in partaking in such a thing would have to pay, so the consumers would get this extra cost which may or may not offset the savings on the reduction of their internet connections.
Biting the hand that feeds IT
