The frog packs have two parts, one is a mineral cartridge, the other is grannular bromine. So in essence its overpriced bromine in a fancy yellow cartridge.
What they don't tell you about bromine, is that it stays in the tub after it gets used up. If you add an oxidizer, you can reactivate the bromine over and over again. Instead of wasting money on more frog cartridges, spend it on either an oxidizing shock with potassium monopersulfate as its main ingredient, or bleach. Both are effective oxidizers and will allow you to reactivate the bromine in your tub. Bleach comes with the added advantage that it is both an oxidizer and sanitizer. Of course then you have to ask yourself if it is the bromine doing all the work or the bleach, and sooner or later you realize that for about $3/gallon, you can't beat bleach.
You could use dichlor as well, but it brings with it all the issues associated with stabilized chlorine. The cyanuric acid level will build up over time and eventually the dichlor will no longer be effective, and you will probably have to replace your water.
I run most of my tubs with bromine and MPS, and for the more difficult tubs (usually rentals that get overused and abused) I will also add bleach. If I were doing it for my own tub, I would probably stick with Bromine and bleach.