Now that allegations of a second high-profile sexual assault on a hotel maid have emerged, New York's Pierre and Sofitel hotels have agreed to give staff panic buttons so they can call for help if they're attacked by guests. The hotel workers' union is working to make these buttons mandatory in all hotels in the city.
Great idea (probably long overdue) but I also think a good old-fashioned can of mace stored in the trolley would do the trick quite nicely. Plus, zut alors, it would probably add some much-needed (and probably quite "foreign" to these eejits) discomfort and humiliation to the equation.
Speaking of equations, how about warning notices on the backs of hotel room doors along the lines of: MACE + FACE = FALL FROM GRACE.