To assist people in practicing mindful breathing and regulate their perceived workload while not disturbing the ongoing foreground task during daily routines, we developed a mobile and personalizable pneumatic-haptic feedback device that provides programmable subtle tactile feedback. The device consists of three soft inflatable actuators embedded with DIY stretchable sensors. We introduce their simple and cost-effective fabrication method. We conducted a technical and user-based evaluation of the device. The user-based evaluation focused on the personalization of the tactile feedback based on users' experience assessed during three pilot studies. Different personalization parameters have been tested, such as two tactile patterns, different levels of intensity and frequency. We collected the participants' self-reports and physiological data. Our results show that the device has the potential of a breathing guide under certain conditions. We provide the main findings and design insights from each study and suggest recommendations for developing an on-body personalizable pneumatic-haptic feedback interface.