I need help with regulating and monitoring internet traffic within my organisation.

We are located in a remote location where cable internet is erratic. So for redundancy we have a satellite internet connection as well. While the wired connection is an unlimited plan, the satellite one is a pay per MB one. Hereafter I shall refer to the wired connection as A, and the satellite connection as B.

Here's what I want to achieve:

1. Give access to the internet to users through a single high power router on which both the internet connections are working.

2. Using A as the default connection for all users. Connection B to be activated only when A is not functioning.

3. Keeping a log of the data usage of each user, filtered by MAC address for the usage on connection B.

4. Some means of letting the user know which connection he is using at any point of time, so that he can regulate his use accordingly.

I have enough machines and can dedicate one for the purpose of regulating and monitoring. I am also okay with purchasing additional hardware or software for this purpose. I have working knowledge of linux and am willing to try a solution on it.
I set up a similar inexpensive backup network gateway to the internet between two sites, and used a piece of software CALLED Alert PING Pro http://www.bestshareware.net/alert-ping.htm. I bought a license of this software to ping over Network A to a destination, and upon a loss of connection with a server at the other end of Network A, a script that I programmed would run and sever the connection with Network A as the Gateway and turn the alternate Gateway connection through Network B which was SLOWER, but kept the food store running until Network A was healthy again in which it would not sever the connection to Network B automatically until after the stores were closed for the evening as for the Point of Sale traffic etc did not like to be severed mid stream of transmissions between sites. Our Network B connection was a private DSL connection between 2 main sites that also had outbound to internet through DSL connection at the remote site which was able to be BRIDGED to the main site.

Basically I had a redundant Gateway where Site B would just about always connect over a T1 to the other site to go outbound over Cable Broadband through Site A. IF Site A lost its internet, I had it set up that the Gateway at say 192.168.1.1 at Site A would be shut down, and then a Gateway at Site B would activate on the LAN at 192.168.1.1 with a gateway for all systems to share through the DSL internet connection at Site B. Since these 2 sites had less than 254 network devices with a network bridge between them this was very easy to do.

Alert Ping Pro works awesome for this type of application and does not cost much. This software also can alert you when the latency gets bad etc, or can kick on an alternate path out to the internet when you have excess traffic that is making things latent.

*There was no notice to the users though with my setup. My setup was to work seamless so that people were not even aware that the one gateway was down. But if someone was downloading something like a 25mb PDF etc, they could probably tell the difference between the Business Class Broadband Connection of around 67mbps download and 24mbps upload compared to DSL which was just 4mbps down and 1mbps upload. I suppose if you wanted to you could trigger a e-mail to people to make them aware of this alternate gateway is active and please limit your internet access to that of which is extremely important.