I was at a restaurant last night where they gave me one of those awful pagers. Not only did it vibrate though, it also repeatedly shouted at me, "Your table is ready." It was disruptive and surely annoyed the other patrons while we settled up at the restaurant's bar and made our way down to the host stand.
It made me really wish I could just get a discreet SMS telling me to take my table.
OpenTable has the advantage too of already having lots of their customers' phone numbers on file, which opens the door to some interesting matching/analytics opportunities.
Restaurant A might want to know, for example, that many of the same customers who walk in to their restaurant make reservations at B & C instead -- perhaps A might want to make changes so that people plan ahead to eat there rather than just walk in.
a) Sit at the bar and order a drink b) Sit in the waiting area and read posters/chalkboards about upcoming events, happy hour specials, gift certificates/loyalty programs, etc.
Either way, the restaurant comes out ahead (especially at the bar, where alcoholic beverage margins make every restaurant owner smile). I wouldn't be surprised if a restaurant saw a decrease in drinks purchased if customers were allowed to freely wander beyond the range of those pager devices.