One of the things we believe helps to increase the number of replies to your questionnaire is limiting the barriers to starting to fill it out. We try to do this by sending, for example, text messages to smartphones, from where the participant can fill out the survey right away. The surveys are always mobile-friendly, which means that they can be easily filled out on a smartphone or tablet.
One of the things we believe can also help are native apps. We have created several apps to make it easier to answer daily, repetitive questions. However, we are also in the process of creating a research survey app.