Table 1 Questionnaire

Memorable experience

Experience

 1 Open question: “Bring to mind a single outstanding positive experience you have had recently with the tracker”

Need fulfillment

 30 Closed questions measuring the intensity of need fulfillment for 10 universal human needs proposed by Sheldon et al. (2001) namely autonomy, competence, relatedness, meaning, physical thriving, pleasure, luxury, security, self-esteem, popularity, response from “very slightly or not at all” (1) to “extremely (5), such as: “During this experience I felt I was very capable in what I did”, “During this experience I felt a strong sense of physical well-being”

Affect

 20 Closed questions, response from “very slightly or not at all” (1) to “extremely (5), such as: “During this experience to what extent did you feel proud”, “During this experience to what extent did you feel afraid”

Usage over time

Expectation phase

 1 Open question: “What were your initial motivations and expectations when purchasing the tracker?”

 1 Closed question, response from “very slightly or not at all” (1) to “extremely” (5): “To what extent did you expect the tracker to impact your life style?”

Initial use

 1 Open question: “Using simple, easy-to-understand terms, what did you initially use the tracker for?”

 1 Closed question, response from “very slightly or not at all” (1) to “extremely” (5): “To what extent do you think the tracker fulfilled your initial expectations?”

 2 Closed questions, response from “Never” (1) to “Always” (5): “In the first weeks of use, how often did you wear the tracker?”; “In the first weeks of use, how often did you look at/reflect upon the collected information?”

Prolonged use

 1 Open question: “Using simple, easy-to-understand terms, what do you currently use the tracker for?”

 2 Closed questions, response from “Never” (1) to “Always” (5): “Currently, how often do you wear the tracker?”; “Currently, how often do you look at/reflect upon the collected information?”