I assume special equipment varies by carrier but if you can't listen to the voice messages, maybe it would be better if you could turn off the voice message ability of your phone and just have a standard message that says please don't leave a voice message, send me a email message etc at
or call phone number 123-4567 to leave me a breal message.
Btw, I had that funny little symbol myself last week, but didn't actually have a message. In order to clear it, I left myself a message and then went into VM and deleted it and the o_o went away ;)
My wife isn't deaf but wears hearing aids and can't really hear well on most phones, so we rarely talk and generally use email and IM, so I understand some of your frustration.