That's our third step though, first our recruiters filter applications (I have no idea how many people are funneled out at this point)

Then we have a 30 minutes phone call to discuss experience and presell the company. We also try to answer all their questions at this point and explain the challenge. Something along the lines of : "so the next step will be a take home test. We just want to see how you code, don't put too much pressure on you, just do your best in the time given"

Historically we have only been looking for pretty senior engineers, although we are relaxing this a bit.

The company has also been sponsoring a lot of visas (even with very interesting salaries, senior mobile engineers are hard to recruit .. most of them are already happy where they are), I think that take home are a good way to handle this case.

The applicant can take the exercise whenever he wants (the only limitation is that we might not be available to answer their questions in the middle of the night) and shows us what they can do.