I spotted this article in the Chicago Sun-Times earlier this week. A "superstar" cop has sued over two years of overtime on his BlackBerry. An arbitrator specilaising in employee relations describes the BlackBerry issue as an "uncharted, undefined area" for many employers.
The irony of this is that sustained email checking via BlackBerry is not great from either employee or employer perspectives: if anything, it reduces productivity, is detrimental to work-life balance and crowds out deep thinking.
I expect we will see more of this in the US with the UK following suit a couple of years from now….