What is the health effect of wireless audio speakers?

I presume you are referring to the electromagnetic fields in the area
of the speakers.  The utilities and communication interests will tell
you the EMF's are harmless.  People who are electrically sensitive
(ES) and have reactions to EMF's at different areas of the
electromagnetic spectrum may or may not be able to feel the infrared
radiation...which would be the central nervous system feeling
agitated.  Another effect is insomnia, also "not feeling like
yourself," although some people get skin rashes.

If I was wondering about the effects I  would first spend time (24
hours) in an environment that was clean of EMF's from either
electricity or cell towers or cell phones or radar or wireless
speakers or even televisions or computers or fluorescent lights or
even land-line phones that give off some radiation from the earpiece. 
This causes the nervous system to level out and calm totally down from
the stimulation from electrical sources that we generally live with
and get used to.    Next become "exposed" to the environment of the
wireless speaker and see if any difference can be felt over the next
hour or several hours...like a feeling of stress or inability to
concentrate or agitation.  If you can't feel any difference then you
may not be susceptible to the "health effects."  Would you put your
babies bed between the speakers?  No.  That is called prudent
avoidance...you can't prove it but you play it safe.  Is there anyone
who is going to be able list some health effects of wireless
speakers....I don't think so but I'll be happy to be proven wrong.