Thanks for asking. It will be for both platforms.
And don't worry we won't ask you to download anything. This research is based more around some of the concepts of the application and what it does as opposed to actual software testing. So this is literally a small questionnaire and that's it. Nothing to fear people
As a side note though we may do actual app testing in the future. But if were to do that it would probably be more local based with people in person as opposed to remotely. If it were a web app we would probably run remote tests but not for a phone/tablet app.