<p>Program and interface: computer.
The creation of the battery and electrical components and the plastics involved with the casing and potential water/heat/pressure resistant parts: materials.
Interaction of aforementioned components: electrical/mechanical</p>
<p>If that’s what you really want to do, you could pick any of the majors, but to get to something so specific you’d have to wait until grad school unless Verizon/Sprint etc. offer you a job after your bachelors.</p>