Table 2.
Characteristics of phase 1 studies (N=52).
| Characteristics | Phase 1 studies, n (%) | |
| Number of surveyed studies or apps | ||
|
|
Android | 45 (87) |
|
|
iOS | 6 (12) |
|
|
Both | 1 (2) |
| Roles of MLa | ||
|
|
Recognition | 19 (37) |
|
|
Detection | 6 (12) |
|
|
Prediction | 4 (8) |
|
|
Recognition and monitoring | 4 (8) |
|
|
Recognition and recommendation | 4 (8) |
|
|
Recognition and estimation | 2 (4) |
|
|
Recommendation and monitoring | 1 (2) |
|
|
Recommendation | 1 (2) |
|
|
Estimation | 1 (2) |
|
|
Recognition, recommendation, and monitoring | 1 (2) |
| Types of ML | ||
|
|
Supervised learning | 39 (75) |
|
|
Unsupervised learning | 1 (2) |
|
|
Both | 1 (2) |
|
|
External ML library | 2 (4) |
| Processing techniques | ||
|
|
Data | 25 (48) |
|
|
Image | 11 (21) |
|
|
Image and calculation | 4 (8) |
|
|
Data and calculation | 4 (8) |
|
|
Voice | 3 (6) |
|
|
Calculation | 3 (6) |
|
|
Image, data, and calculation | 2 (4) |
| Focus | ||
|
|
Physical health | 19 (37) |
|
|
Weight control | 14 (27) |
|
|
Disease | 9 (17) |
|
|
Mental health | 5 (10) |
|
|
Sleep | 3 (6) |
|
|
Recipe’s recommendation | 1 (2) |
|
|
Multidimensional | 1 (2) |
| Crucial functionalities | ||
|
|
Recognition | 20 (38) |
|
|
Detection | 9 (17) |
|
|
Prediction | 4 (8) |
|
|
Recognition and recommendation | 4 (8) |
|
|
Recognition and monitoring | 4 (8) |
|
|
Recommendation and monitoring | 3 (6) |
|
|
Monitoring | 3 (6) |
|
|
Recognition and estimation | 2 (4) |
|
|
Estimation | 1 (2) |
|
|
Recommendation | 1 (2) |
|
|
Recognition, recommendation, and monitoring | 1 (2) |
| UIb components | ||
|
|
Label | 18 (35) |
|
|
Image | 17 (33) |
|
|
Button | 15 (29) |
|
|
Input box | 8 (15) |
|
|
List | 8 (15) |
| Navigation and structure | ||
|
|
Tab | 6 (12) |
|
|
Back and next | 5 (10) |
|
|
Main page | 2 (4) |
|
|
Tab and back and next | 1 (2) |
|
|
Tab, back and next, and hamburger menu | 1 (2) |
| Services and technologies | ||
|
|
Motion sensors | 21 (40) |
|
|
Camera | 18 (35) |
|
|
GPS | 2 (4) |
|
|
Microphone | 4 (8) |
| Security features | ||
|
|
Log-in | 1 (2) |
| Architectures and patterns | ||
|
|
Client-server (web-based) | 30 (58) |
|
|
On device (offline) | 19 (37) |
|
|
MVCc | 2 (4) |
| Inference of ML | ||
|
|
Web-based inference | 18 (35) |
|
|
Offline inference | 10 (19) |
|
|
Both | 3 (7) |
|
|
Web-ready solutions | 2 (4) |
| Development approach | ||
|
|
Prototype | 8 (15) |
|
|
User-centered design | 2 (4) |
|
|
Agile | 1 (2) |
|
|
Extreme programming | 1 (2) |
|
|
Iterative | 1 (2) |
| Logging mechanisms | ||
|
|
Automatic | 24 (46) |
|
|
Manual | 24 (46) |
|
|
Both | 4 (8) |
| Evaluation | ||
|
|
Algorithm’s performance | 30 (58) |
|
|
Algorithm’s accuracy | 9 (17) |
|
|
Algorithm’s performance and cross-validation | 8 (15) |
|
|
Usability study | 4 (8) |
|
|
Cross-validation | 1 (2) |
aML: machine learning.
bUI: user interface.
cMVC: model-view-controller.