Yes you can!
Yes! If you have a smart phone, then it is still possible to compete. For iPhones you will need the Apple Health app downloaded. For Android phones, you will need the Google Fit app downloaded. When you join a challenge, you will be prompted to choose which app you want to connect with.
Read more information on connecting to Google Fit here.
If you are in an employer sponsored challenge and cannot download Apple Health or Google Fit, you can still participate by adding your entries manually! Learn about manual activity entry here.