I just picked up GHL Doser 2, I looked at the Pacific Sun but was turned off by the 180 page thread on reefcentral dedicated to firmware updates. GHL Doser 2 has had 2 firmware revs since it came out and has gotten great reviews. I just got this and setup last night, and yes you do need a pc with usb cable to get setup initially then you can setup wifi and setup program on pc to connect through wifi. If you arent PC savy, then you could have issues getting firmware upgraded. The software does easily let you calibrate each channel, so you are sure what your exact flow rate is with the liquid and tubing arrangement you are using. Anyways, I think its a great unit, was kind of pricy but hey, what isn't pricy in this hobby. I like the idea that I can easily log into it and change the daily dose amount up or down and have it adjust the schedules (up to 150 dosing times a day) automatically and amount needing to be dosed per dosing.
Also, I am an iphone guy and they have posted screenshots of the iphone app on their forum, its coming soon, likely within the next month. Once that comes in, I will be dialed in!!! Can't wait.