What about something like a low dose of Ritalin (low enough to just encourage focus, not force it) and then a time released reward circuit promoter to positively reinforce the focused behavior pattern that the Ritalin helped bring about. Tie the focused behavior to some sensory stimulus (Pavlov's Buddhist attention bell) by association. Then, over time, make the positive reinforcement a bit random and intermittent to exploit that same hook you mention and back down the Ritalin dose to zero as the behavior pattern takes good root. (In retrospect, maybe I learned the wrong lessons from Brave New World. :-)
Like noted above Skinner found out that random rewards are much more addictive than predictable rewards. So to make something less addictive you need to make rewards more predictable.
So the tip about checking email (or whatever) a few times each day or in specified intervals is generally good as this will make rewards more predictable and less addictive.
One, finding the right dosage is a trick all by itself; two, Ritalin does not force focus. It ups the level of dopamine available to the brain. An improved ability to focus may be one of the results, but (sadly) it's not so predictable.
Sometimes that's how things work for me. If I can just get myself over the aversion hump I'm often then able to get on a roll and keep going. By then there's a workable feedback loop of effort and results.
Kathy Sierra has written on how this theory applies to Twitter, which is worth a read: http://headrush.typepad.com/creating_passionate_users/2007/0...
Solving this issue is probably hard since it's followed by humans and animals... So it must be programmed deep into us.