Braun claim that two of their epilators are suitable for facial use:
http://www.braun.com/global/female-grooming/silk-epil-epilators/silk-epil-9/silk-epil-9-models.html
They also include this information on their website:
"Will more hair grow back if I epilate?
No, this has been proven in dermatological tests. In fact, studies show that ongoing epilation reduces the amount of hair re-growth, making them lighter, softer and fine, with a semi-permanent effect. Say goodbye to stubble that’s rough and hard and hello to 4 weeks of smoothness".
OK, of course Braun aren't unbiased but given (a) their reputation ; and (b) the strict controls on advertising claims these days, the evidence they cite from 'dermatological tests' might have some validity to it.