Python is great for prototyping, but my grand plan with this project is to add more sensors, integrate with some "smart home" devices and create a web UI - and I'm more comfortable coding all that in Java.
This is not only an Android problem, Apple is equally guilty of this. Arguably, more so.
Nor is it a Java problem. Some extremely speed-sensitive high perfomance code used by high speed trading algorithms use Java. This is in an environment where micro-seconds count.