Mobile phones are a widely used platform for educational apps, mobile health, and a variety of chemical tests. Here, we are working on a mobile phone-based physics lab (mPhysics) that uses a mobile phone's capabilities to run simple physics experiments and demonstrations. While a mobile phone can be used to analyze magnetic and optical properties of materials using built-in sensors, thermal analysis has never been incorporated into a mobile phone. Here, we propose to integrate thermochromic sensing with the image processing conducted on a mobile phone for in-class or in-lab demonstration of thermal properties of materials. We make inexpensive and nontoxic materials based on polydimethylsiloxane (PDMS) mixed with a thermochromic pigment that changes color from blue to white when heated. This material can be used to visualize such phenomena as change of temperature, thermal conductivity, and heat capacity. Then, the smartphone camera and a custom app can be used to track local color changes and translate them into different thermal properties. We propose to use this approach for experimental education of high school and undergraduate students.