I don't know about droidjack specifically, but your phone is not at all secure, particularly for android. All it takes is a little bit of bad C code to cause an overflow of some sort. Combine that with widely available unencrypted firmware and you have a real vulnerability.
Are you implying that you could create an Android exploit with "little bit of bad C code"? If so, I'm not sure you understand how exploits work and the work required to get around all of the mitigations in place.
