Almost everybody has a cellphone they use for business, making calls and sending text messages to customers and suppliers so work gets done even when they’re out of the office.

Perfect. Just let them get on with it. Why bother introducing a convoluted policy to monitor and manage staff mobility? Because it isn’t that easy, of course. At the very simplest level, a company must figure out how to reimburse staff for the business calls they make, either through an allowance or by picking up their entire phone bill.