GSM Trinket, developed by sjobergsson.se, is an Android application designed to control GSM-devices through SMS-commands and DTMF-commands. The app looks like a trinket with buttons, and it allows you to add multiple trinkets to control multiple GSM-devices, which you can switch between by sliding the screen. You can add, edit, or remove any SMS-command and DTMF-command, and even set up a schedule for any SMS-command by days of the week.

The app provides a range of features, including the ability to protect it with a pin-code or fingerprint, set up notification repetition for unread messages, and select the sim-card for sending SMS-commands to each GSM-device. Additionally, if your GSM-device sends its location, you can see its position on the map. Please note that since January 1, 2019, publishing applications that use permissions to send and receive SMS-messages is prohibited, which adds some limitations to the app's functionality. Install the app to discover what you can do with it.