In Philadelphia, the crowd was wearing those bracelets, and they would light up at applause points. When Harris would continue speaking, the light would go off. I suppose they could have been for effect, but seemed to be more like personal 'applaud now' indicators.
For what it's worth, I just checked the DeCamp book [Franklin Cover-Up], and there is no mention of Walz. Not surprising though; there is a lot of good information in it, but the book, seemed to be somewhat of a gatekeeping effort, limited to exposing only certain individuals.