this is databox 0.5.2 (plus some fixes) and android app 0.5.7.
the sensingkit client in the phone app only sends data when the databox app is in the foreground and screen is on. If the app is moved to the background or the screen is off then it does not send data. (i've tested with light, step count & acceleration)
(It does send data with lock screen visible and the app underneath it.)