Is there a silent device you can use to signal in a meeting that you
want to ask a question or make a comment.  The moderator would then
call on you.  Perhaps a light you switch on or something that glows??

Hi! Thanks for the question.

You can use the following gadgets. I searched for things that has an
on and off switch so it lights up only when you want it to. I will
direct you to the Froogle search results so you can choose from a
variety of products.

Light Pens
://www.google.com/froogle?q=light+pen+switch&btnG=Search+Froogle 

Light Sticks
://www.google.com/froogle?q=light+sticks+switch&btnG=Search+Froogle

Flashing Keychains  
://www.google.com/froogle?q=flashing+keychains++&btnG=Search&as_qdr= 

Keychain Flashlights
://www.google.com/froogle?q=keychain++flashlights&btnG=Search+Froogle 

Flashing Rings (Not a Froogle Site)
http://www.flashingblinkylights.com/stores_app/browse_dept_items.asp?page_id=17&categ_id=3&parent_ids=0

You can also use simple lighters as well.

Lighters
://www.google.com/froogle?q=lighters&btnG=Search+Froogle 


Search terms used:
things that light up in the dark

Searched at Froogle:
Light pens flashing rings keychains

I hope these links would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
                             
Thanks for visiting us.                              
                              
Regards,                              
Easterangel-ga                              
Google Answers Researcher

The most effective way in which you can draw attention to yourself
silently is to stand on your chair and disrobe.

You will be surprised at how much support you will get from other
attendees who, typically, will encourage you with cries of "Get 'em
off!"

I like the lighter idea. Its like an Air Supply concert, where
everyone is swaying and putting their lighter in the air....

I never went to it, uh, I saw that on TV, yeah that's the ticket!

And in what way is raising one's hand not silent?  Just don't utter
"Ooh, ooh, tecaher.  Pick me," as is done by school children.  Simply
raise your hand and wait for the moderator to recognize you.  No
technology needed.  Inexpensive.  Take it anywhere, even to the beach.
 (OK, I'll stop now.)

^^preposterous.

Just stop snapping your fingers   ;)
Seriously, I suppose you want to avoid calling other
listeners'/participants' attention to yourself, just let the moderator
know, right?
Isn't that a little unfair in an open meeting?  If it is a larger
gathering, the moderator would probably be keeping a mental or written
list of the order people had raised their hands and would be trying to
call on them in that order.
If you used a discrete device, when he called on you, others would
think that he was favoring you by letting you jump the line, so maybe
he would not, or to clarify your signal would ask you when he saw it,
thereby letting others know that you were in the line.
Of course, if you were the specialist on the subject invited to
provide your expertise, he and you might want a discrete signal, so
that you could let him known when you wanted to join the discussion,
and then he could turn to you and say: That's a good point.  I would
like to hear r2-ga's opinion.

(Don't be bothered by Probono's suggestion. He's a little frustrated
today 'cause he can't find the kind of questions that he really likes.
 :)  )

i feel that r2 was trying to find a solution, rather than trying to
search for devices that light up.IMHO i dont think its a good idea to
start flashing lights on my pen so that the person chairing the
meeting can take note of you. instead of raising your hand, maybe
there can be a subtle gesture you can do so that at an appropriate
time you can be called upon to voice your opinion? just wondering..