Yes. The Dexcom transmitter communicates directly with your compatible mobile device, even when it is paired with the t:slim X2 pump.
The Dexcom transmitter can be paired with one medical device and one non-medical device at the same time. (e.g. A transmitter can connect to your t:slim X2 Pump and a mobile device running the Dexcom app, or to a Dexcom receiver and a mobile device running the Dexcom app.)
Important note about Dexcom support:
Dexcom and Tandem have agreed which system issues are best handled by each company, including which company is responsible for reporting those events to the appropriate regulatory authority. To help ensure that the required reporting takes place in a timely fashion, customers may need to contact Dexcom for some issues and Tandem for others.
Tandem handles issues with the connection between your Dexcom transmitter and t:slim X2 pump, questions about calibration, the “---” display, and sensor failures after the 2-hour warmup period.
For all other CGM issues, including the sensor failure during the 2-hour warmup, “no restarts” alert or physical problems with your sensor or transmitter, such as bleeding, bruising, skin reaction, adhesive issues, applicator issues, or broken wires, you should contact Dexcom using one of the options at dexcom.com/contact.