Technology Acceptance Model for Mobile Services as a Design Framework - Human-Computer Interaction and Innovation in Handheld, Mobile and Wearable Technologies

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has total control over the data. All data are stored

locally in the mobile phone, and thus can be ac-

cessed, viewed, modified and deleted at anytime.

The users can transfer their WD data wirelessly

via the Multimedia Messaging Service (MMS),

Bluetooth, or email to researchers, experts or

peers. Also a two-way data synchronisation was

enabled between WD and its web-based counter-

part, Wellness Diary Connected (WDC; Nokia

Corp., Helsinki, Finland). In this case, user's data

is secured and can be viewed and manipulated by

the user also in the web service. All modes of data

transmission from WD are user-initiated to ensure

the user's control over his/her data. These choices

were made in order to increase the users' control

and ensure their privacy, and thereby enhance

their trust in the application.

A trust-related design decision was to protect

users from their own, over-ambitious targets. Goal

setting was designed to enable the user to commit

to a change by setting personal targets. In order to

prevent unrealistic targets, an algorithm to check

the weight target for safety was included. The

algorithm checks the user's target against healthy

BMI limits and weight management recommenda-

tions. The rules aim to discourage underweight

users to lose weight and to discourage normal or

overweight users to gain weight or lose weight

too dramatically. This feature was designed to

help the user avoid potentially unhealthy targets.

Another trust related design target was prevent-

ing user errors. A simple validation mechanism was

designed to prevent the user from unintentionally

saving empty entries. The application detects if a

mandatory field has not been filled in and asks the

user whether he/she really wants to save the entry.

Taking a new application into use is always a

challenge requiring learning and should be made

as effortless as possible. To facilitate the adoption,

the first versions of WD were integrated into the

standard Symbian Series 60 calendar. This design

provided users with a recognisable user interface

and a familiar way of using the application. In later

versions, the calendar integration was redesigned

in order to emphasize well-being management.

Still, sharing data between WD and the calendar,

calendar-like usage logic and many calendar-like

views were maintained. Another motivation for

the calendar paradigm was to provide a fit to the

existing usage culture of the mobile phone (daily

time management) and an opportunity to extend

it to daily well-being management, following one

of the TAMM design guidelines for facilitating

adoption.

The user acceptance of WD was evaluated in

three user studies as detailed in Table 10. The user

acceptance of WD in these studies was examined

based on the dimensions of TAMM, perceived

ease of use, ease of adoption, value, and trust.

Perceived ease of use of WD was high in all

studies. In Study I, about 90% of participants

perceived WD as a simple application and in Study

II, 100% of participants reported that it was easy

to make entries with a mobile phone. In Study III,

WD was perceived as easy to use by 60% of re-

spondents.

Table 5. User acceptance of the wellness diary was studied in three field trials

Health issue targeted

Population

Participants

Duration

Study I: Weight management (Mattila et al.,

2008)

Working-age adults, mean age 40

years

30 (21 males, 9

females)

12 wk

Study II: Occupational rehabilitation for stress-