[i have never seen of heard anything about that meter - that doesn't make it good or bad - sometimes it is worth spending another 20 to 50 dollars to have an accurate and reliable piece of equipment - such as the american marine meter
you don't necessarily have to have one, but if you are planning on using a calcium reactor, it is really a must for safety - they are great and take the guess work out of testing, so, if you have the $$, i would recommend getting a good quality one.
here is a link: http://www.championlighting.com/e/env/0001mv0G1o0QU0UECI5c2R3/Products/Controllers/AMcon.html?link=/Products/productinfo.html&item=mainhm_