I have decompiled the apk and it produced a somewhat useful (but incomplete) package of Java source files, which can be useful for reverse engineering the serial protocol. For example:
<string name="parse_block_tag_ping"><U>Ping</U=db></string>
...
private static final byte[] f2305f = "getCAN ".getBytes(Charset.defaultCharset());
private static final byte[] g = MyApp.a().getString(R.string.parse_block_tag_ping).getBytes(Charset.defaultCharset());
private static final byte[] h = MyApp.a().getString(R.string.parse_block_tag_startu).getBytes(Charset.defaultCharset());
private static final byte[] i = "<request>Unknown</request>".getBytes(Charset.defaultCharset());
You can do the same, or alternatively ping me if you'd like me to email you the source package.