The Lumin screen uses a variety of apps we have developed in-house for our customers. We made it not possible to download external apps (eg. from the App Store or Google Play) since we designed Lumin to work the same way and be easy to use.
If there is any app you'd like added, please give us a call as we might have something similar for you. You can email our support team at firstname.lastname@example.org or call us at (03) 8899 7525.