Hi, that's an interesting project you've got. Also, your price tag is way too high, I'll take this project for, say, $70. So, I have everything I need right there: a similar single board computer and a bunch of electronic components. I played with "DIY surveillance" systems so I could offer you some extra features if you're interested: tons of configuration options, or maybe a live web-server or something crazy if you want it. I'm quite enthusiastic about your project TBH, it would be a lot of fun for me.
Feel free to ask for a demo.