When I first saw the 'belly dancer' term here, I couldn't help thinking of the bizarre treatise on belly dancing swords which was proposed seriously some years ago, but was really pretty hard to take seriously
However, I suppose when studying weaponry, there is a degree of application that must be considered from the costume and ritual perspective.
With that, it is interesting to see that this item is shown as a womans knife, and from Bagabo, while as also noted, wider range of use must be considered.
These bells are known throughout Asia as 'tiger bells', and while apparantly produced largely in China, they are widely distributed, and thier use is found in many applications...including dance accoutrements. While not of course, 'belly dancing' necessarily, these sound producing bells are found in that as well as many kinds of dancing.
I found the information on these bells when recalling that these were also seen on some kampilan, and in this case, appear to have been regarded as auspicious and attached to the hilts. In the case of these, there do seem to be instances noted in Mindanao ( the knife here is from Bagobo in SE Mindanao), as well as in Indonesia and Malaysia (Sarawak).
In many instances these bells are used in amuletic sense and by shamans, and of course in many cases these are placed on animals, so it seems the uses of these range from novelty to auspicious features.
Attached is a plate furnished by Maurice and a kampilan posted by Gav, both in November, 2009, which I found by using the search feature here.