is there also a button marked "infinite improbability drive" ?

My guess is that this thing died a long time ago.  It makes no sounds currently with the blinkers or anything else.  Having a speaker facing upwards and some rain or whatever may have killed it.  I am going to be pulling this device out of my wiring to avoid it shorting things out later.

I just think its a funny thing to find on my bike.  I was half expecting to find a flux capacitor beside it.

You can buy piezo buzzers that will fit inside the turn speedo tank panel; thus, out of the weather.   Radio Shack has them as well as other sources.   You can either buy 2 units, one for each R & L indicator bulb, or 1 unit and two isolation diodes like a 1N4001.  The diodes can be had for about 10 cents each and are 50V PIV rated, so save you a couple of buckeroos over buying two buzzers.   The turn signal circuit is hot up to the switch, so they need to be placed on the bulb side (switched side) in parallel with the speedo panel indicator bulbs themselves (switched 12V to ground).   The one here only draws 10ma @ 12V, so wouldn't pose a significant additional load on the fuse or flasher, and gives you 76db of beep sound; about as loud as a vacuum cleaner.   There are others that go up to 90db; i.e., weed eater level.

http://www.radioshack.com/product/index.jsp?productId=2062397