can this product be used to enhance yeast activity when making bread ?

I'm not sure I would use it in your application because, your going to consume your end product. In my application the only thing consumed was a by-product of the yeast and yeast nutrient.

What do the tablets do?

Campden tablets (potassium or sodium metabisulfite)[1] are a sulphur-based product that is used primarily to sterilize wine, cider and in beer making to kill bacteria and to inhibit the growth of most wild yeast: this product is also used to eliminate both free chlorine and the more stable form, chloramine, from water solutions (e.g., drinking water from municipal sources). Campden tablets allow the amateur brewer to easily measure small quantities of sodium metabisulfite, so it can be used to protect against wild yeast and bacteria without affecting flavour. Untreated cider must frequently suffers from acetobacter contamination causing vinegar spoilage. Yeasts are resistant to the tablets but the acetobacter are easily killed off, hence treatment is important in cider production.