This article discusses a trojan that is present on an android phone app, and, in a rather morally abhorrent fashion, disguises itself as a diabetes help app. The app seems to function like as expected as a regular health app but, in the background, an old method of sending an SMS code to a trojan dialer is used to forward information (usually financial) to said dialer.
https://www.fortinet.com/blog/threat-research/android-malware-targets-diabetic-patients.html