Add option to not check/download updates automatically when using mobile broadband

Binary package hint: update-manager

I would like to have a checkbox option in Software Sources that would say:

[] Don't check and download updates if using mobile broadband

In many countries bandwith is still expensive when using mobile broadband (eg. here there are no flatrate options and the smallest data package is just 50mb, even with HSDPA coverage). I don't want my bandwith wasted on checking for updates and downloading them automatically, so every time I switch to mobile broadband I have to remember to change the settings in Software Sources. This should be handled automatically with an additional option.

I think PackageKit gained this functionality recently, but despite initial enthusiasm there has been no push to actually replace Ubuntu's tools with a universal solution that would benefit all.