I bought one of the atama sesame bluetooth LE dongles; don’t bother. It has an integrated chirper that fires randomly and only works on one Mac at a time; that is, when it works at all. I set mine for low signal (be as far away as possible) and just sitting at my Air, it would randomly lock and unlock my screen. I replaced the battery to no avail; I did, however, unsolder the chirper, so I’m sure I’m well outside warranty service.
