Need a firewall recommendation - some specific requirements

[pchartwell]

I have a situation where I am being asked to only allow 'unlimited' internet access to a select group of users. For the rest, they are to request internet access and the approver should have the ability from their workstation to give access to that specific user account (or machine, etc). Even better if the approver doesn't have to remember to shut off the access later but can set a length of time (1 hr, 1 day) for the access to be on and then return to a disable default automatically.

What are some hardware or software firewall and/or applications which could be used for something like this? Any advice and suggestions appreciated, thanks.