This does not sound like it could be possible in thunkable x, although, if you handed it out to users with android devices and use an android app builder to achieve this.
Then for the workers with iphones, if you could spare them an android device and let each worker have it for a day to use the app.
Im sure there are built in solutions or even extensions. Check out kodular, it is a fantastic android drag and drop builder, it works the very same as thunkable and ai2, only there are far more built in blocks and it supports the same extensions that thunkable and ai2 do (aix).
(edit)
you could have it so the person must have the app open the entire time but this could be bad for organic displays and screen burn in. There is a notifier in kodular that i believe can be operated by the device, so it could run in the background and send a notification every 15 minutes.