Table 2.

Themes related to limitations of the existing app.

Themes	Health care professionals (n=10)	Inpatient participants (n=5)	Outpatient participants (n=5)
Design of the app	“Buttons were too small” making them “easy to miss” [Participant 2] “Press a few times, will add on to the reaction time” [Participant 1] “There is no try out to understand how it works.” [Participants 3 and 5]	No mention	“More instructions”[Participant 2] “When I got things clear, I focus on star” [Participant 5] “No design or anything” [Participant 1] Buttons to be “bigger” [Participant 1] “Joystick interface” to indicate a response [Participant 2]
Visual probe tasks	“Too many repetitions” [Participant 2] The task was “so fast” [Participants 3 and 5]. “Distinguish the frame from one another looking at the asterisk” [Participant 1] “Focusing on the asterisk only.” [Participants 3 and 7] “Pictures were so fast, after a while, I stopped paying attention and just look for the asterisk” [Participant 8]	“Were too fast” [Participants 3, 5 and 7] “My mind cannot catch up, fingers cannot catch up” [Participant 5] “Repetition is the same” [Participant 5] Task is “too tedious” [Participant 3]	The trial was “too long” [Participants 1 and 4] “Too fast” and “quick” [Participants 2, 4, and 5] “I never even have a chance to see” [Participant 1] “Too fast. My mind was to aim for the star. The pictures I was not interested.” [Participant 4] “It is too fast that we don’t really see the picture” [Participant 3]
Images included in the visual probe task	“Image colour does not stick out” [Participant 3] “Non-white background will enhance the focus of the images” [Participant 2]	The “colour is dull” and “the images are repetitive” [Participant 1] “I see the same image for 30 times or more” [Participant 1]	“Keep seeing the same pictures” [Participant 3] “Very boring, put more pictures” [Participant 1] “Maybe more picture, very repetitive. I keep on seeing the same pictures over and over again” [Participant 2] “It comes in pairs. It always weed and chocolate cake. You can figure out” [Participant 2]
Safety of administering the app	No mention	No mention	“Triggering. Like I think just keep seeing pictures of drug of choice” [Participant 2] “Early recovery is triggering. For myself, if I am in detox, might trigger me.” [Participant 5]