I use the Hanna tester for DKH Alk. I have cross referenced it with salifert and it is pretty much spot on. I also use one for Phosphate. It is evidently accurate as well, but I cannot confirm personally as I have GHA pretty good at the moment and it registers 0. Clearly P04 is NOT 0, but algae is consuming it. I have the regular one, the 713, not the ULR (ultra low range). Don't bother with the Cal. It is universally understood to be utterly useless.
Beyond that, you could look at the iDip.