I have used three different pediatric dose calculators, and here are my reviews:
Peds Meds
I started with this one because its the one that I like the best and am currently using. I choose it over the others for 3 main reasons:
1) It's very flexible - before I found Peds Meds, I was using two different peds dose calculators since neither of them had a med list that covered all of the medications I wanted. Peds Meds has a pretty extensive initial meds list, but also let you create your own medications! I don't know why no one else is doing this. I actually created a whole category of outpatient meds that I commonly use (the app focuses in on inpatient meds) and emailed it to my friends.
2) The interface is very smooth - it nice to use even if you never use the editing function
3) It got accurate weight estimation - it estimates weight based upon age, but instead of using a poorly validated formula, it uses an actual look up table of CDC data on kids weights.
Pedi Stat
This is my second favorite, and the one I was using before switching to Peds Meds.
Pros:
1) Also supported weight estimation from age, but with the caveat that I think it is formula based. I did a presentation as an intern one point one the accuracy of the various age and length based formulas and basically they aren't as good as one might hope.
2) Very pretty interface
Cons:
1) While pretty, I also found the interface very confusing at times. It can be a weird combination typical iphone tables along with weirder accordion menus and toggle menus. I find that I sometimes get lost.
2) No search feature. I was looking though the tables trying to find prostaglandin dosing, since the category isn't obvious. The app needs a comprehensive search function like Peds Meds has.
Pedi Safe
This was the first app I bought for peds and I think it is the most basic of the three. No weight estimation (it has Broselow colors, but if you have a Broselow tape why would you need a iphone app?). It is essentially a Broselow table in your pocket, it lumps kids into groups by weight (e.g. 24-29kg) which is a bit less precise than I like to be in the practice of medicine.
Hope that's useful!