I actually just had a good discussion this past weekend with the owner of black Jungle on this exact topic and was told that the calcium would need to be ingested to get to the blood cells that would benefit the frog. Since I have no knowledge of how this process works I myself have used the liquid with a dart frog recently with no ill effects so far.

What brought this on was a dart having seizures which is a sign of calcium deficiency or other supplement missing from the diet.
Since the initial calcium and supervite bath and upping the calcium dusting to daily she has had no more seizures.