My friend did a DIY Sous-vide towards the end of last year, no android app, but has a simple UI for set point and tuning.

He actually made it a mains plug pass through (UK version) so that you can use it with a traditional slow cooker for some temperatures etc.

Blog link: http://rfwebb.com/projects/sous-vide-part-2/ Extra pictures (Skip all the PCB ones): http://imgur.com/a/aG1Jp

Edit: source code: https://github.com/bitdivision/sous-vide