I've had a Cl based pool with a SWG for a few years now and have had no trouble with that. I use a Taylor K-2006 for testing.
I now have to figure out how to balance a spa. This spa specifically prohibits the use of Cl (although I assume that refers to hypochlorous acid and not Cl- ions). I understand the idea of creating a reserve of Br- ions in solution and then using some type of oxidizing agent (bleach, trichlor/dichlor, potassium monopersulfate, etc.) to generate the actual hypobromous acid sanitizer.
My problem is that I do not see any test kits that give me the info I need. It seems that I would need to test for 1) sanitizing bromine (hypobromous acid), which is what I believe the DPD test does (multiplied by 2.25 since it's calibrated for Cl) and 2) Br- reserve bank concentration. I intend to start up the spa with some NaBr and then oxidize it. If my DPD test comes back low, how do I know if I need to add more Br salts or if I just need to oxidize existing Br? Is it possible to get a good test for Br- ions in addition to the DPD (which as I understand it tests for hypobromous acid)?