I find the use of cell phones as pocket watches tacky. As a grad student, I've seen many speakers come in and open a cell phone in the middle of a talk to check their time usage, which I find utterly unacceptable.
Depending on your situation, look around a bit and see who's wearing a watch. It may not be the norm anymore, but it's still not an unusual thing to do at all. If nothing else, they are a good fashion accessory.
Don't you think 'utterly unacceptable' is a just little harsh, remembering that technology, fashion, and language are not fixed things and are always changing. I think it is quite acceptable that mobile phones have replaced wrist watches. Or maybe we should go back to giving lectures in a top hat and monocle, and checking our time usage with a fob watch? ;)
It's not the change in fashion that I'm taking issue with. Standing in front of a group of people with your attention fixed on a communication device is not good presentation. If it were glancing down at a clock sitting on a podium or table, that would be fine. This is not how it happens in practice. The biggest difference between a cell phone and a watch or other timepiece on a surface is that a cell phone requires interaction to extract the time. The extent of that interaction really doesn't matter. It goes from a momentary action of pulling a phone out and pressing a wake button to a nervous speaker confounded by a single button press and a screen too dim to see without making a spectacle of the action. This is the more common of the cell phone users I witness. The trouble is that every minute thing a speaker does is on display and just as a speaker expects (or hopes for) respect from the audience, I as an audience member expect the speaker to be attentive and professional.
So can it be done gracefully without my ire? Probably. I have yet to be pleasantly surprised.
I normally wear a watch, but still use my phone's stopwatch to keep time during a talk. I find that looking at a stopwatch during a presentation requires less mental distraction than: (i) keeping track of the time at which my talk started (I am talking about conference talks where the talks usually start a few minutes later than the scheduled time), (ii) looking at the current time and calculating how much time is remaining (it usually takes less than a second, but it is more time consuming that a tap on my phone).
The trick is to disable your phone's auto lock, open the stop watch and run it. That way, you can just tap the screen (I am assuming iphone like smart phone) to see the current time. I think this can be done as discreetly as checking my watch.
The biggest advantage of using a stopwatch is that it provides evidence of how long you have been speaking for. I have had cases where the previous speaker overshot his/her time and a session chair tried to get back on time by cutting time from my talk. In such cases, I have had to point to my stopwatch to say that I still have more than five minutes left. (Usually the talks are twenty minutes, so having five less minutes is a big deal). This (a session chair punishing me for the previous speaker's tardiness) has happened twice to me in the last year.
It was loaned, I had no idea it was so expensive. Good design, though. The stopwatch can be 'pumped up' in 5 minute increments to the time for one's talk. All there, nothing else to fiddle with.
Slight off topic, but I am always puzzled how most conference rooms fail to have a large clock at the back of the room such that a speaker can easily see how they are tracking for time.
If not at the back of the room, a large display at the foot of the stage facing the speaker - the way TED talks display the time to the speaker.
If meeting rooms can remember to embed projectors and speakers in a room, putting a clock on the back wall can't be that difficult.
Depending on your situation, look around a bit and see who's wearing a watch. It may not be the norm anymore, but it's still not an unusual thing to do at all. If nothing else, they are a good fashion accessory.