Been using a similar (but much cheaper) DIY system in our 400G hot tub for some years now .
I just use a small peristaltic pump system hooked up to a timer . Its a very small peristaltic pump (designed for saltwater/reef fish tanks) and dispenses 1.1 ML per MINUTE .
I have it hooked up to dispense 8.25% bleach for approx 15-20 minutes twice a day (for our hot tub normal usage) . The small pump we use dispenses VERY small amounts VERY slowly, so the amount just gets controlled by a timer. Literally, it is just a drop of bleach , maybe every 2-3 seconds ! The peristaltic pump is perfectly timed to kick-on when the filter cycle is in operation , twice a day .
I have hooked it up to various parts in the hot tub plumbing over the years , but the bleach is too caustic, and can cause damage . I finally drilled a small 1/4" hole at the top of the filter "scoop" area , but under the lid(so it cant be seen) . I protrude the small 1/4" feed line though the hole (fits snug) and it slowly drips bleach directly into the turbulent filter box water as the pumps run in filter mode .
I just use bleach bottles direct . 1/4" tubing sticks into the bleach bottle, up to the small peristaltic pump , then out to the hot tub .
This is the pump I use .............
http://www.bulkreefsupply.com/brs-2-part-doser-1-1-ml-per-minute.html
I have two of these pumps, so I have a spare back-up in case one fails , but I haven't had to use it . Been running the hot tub for a few years now like this, and it works perfect ! These little pumps, with the Santoprene tubing can handle the bleach just fine.
I go through approx 1 gallon bottle of bleach every other month .......usually slightly longer . Great when we go away for vacation , and daily use . I don't have to do much for maintenance besides test water parameters once in a while. , to see if the pump timer needs to be changed a little once in a while, but its rare. Once its all set-up , it works pretty well .
I have had the pump hoses go bad occasionally , but they are cheaply replaceable ($12.99 each) as well (They kind of get "sticky" and soft after about a years use). Once every few months I do clean out the 1/4" lines as they can clog with bleach residue . PH does seem to climb slowly , so either I drain and refill every few months , or just add some muriatic acid in SMALL amounts to bring it down once in a while.
Been working great for some years now ........... Love that I dont need to add clorine/bleach on a daily basis. Our hot tub is crystal clear ALL the time !
Can take some pics of my set-up sometime if you are interested . (Whole system is enclosed in the hot tub shell, so may be a few days before I get time to access it again) .