I'm aware that both CockpitWeb.com and PilotAptitudeTest.com have a substantial amount of questions available on Maths and Science questions.
CockpitWeb.com have Numerapt? It may be a bit outdated for you, but to be quite frank, maths and science questions have always remained the same so shouldn't be an issue. You've gotta install this on a PC I believe.
The 'Numerapt' app is fairly expensive, but CockpitWeb have been around for years.
PilotAptitudeTest.com have a demo video on YouTube that shows how they display their explanations to their questions also, which looks very promising, a simple search for 'pilot aptitude test' will yield the results you are looking for.
It would appear that they also have an iPad App, and from reading their FAQ, the questions seem to be based very accurately on the real-life counterparts.
Lastly, when I studied for a PILAPT test, I used a product by a company called FlightLevel360 Software (if I remember correctly) which included maths practice, although not sure if they are still around, again, a search for this will yield results.
To be quite frank, I have used LatestPilotJobs.com in the past specifically for the maths questions when preparing for airline assessments, and whilst the quality of questions are good, they could do with upping the quantity.
Also strongly recommend heading to your local library, given the questions used for Maths and Science testing are fairly uniform across the board when it comes to job applications. There are specific books for these, and a large variety available. Plus, borrowing books from a library are free.
**Edited to Include: How about the OAA Maths CD-Rom? Not sure if available in App Format, but worth a try.*