What should I use?
Common sense.
If you are in "grade school" (ie, high school or lower); quit putting expensive junk in your locker (leave it at home), carry the rest around in your backpack, and keep an eye on your pack.
If you are at a University or College, I am sure someone somewhere sells insurance for dorm rooms and contents, similar to renter's insurance (and if not, that may be a interesting and fruitful niche product you might want to get into if you can find the capital to start it up!).
If you live in an apartment, get renter's insurance. If you own a home, make sure your homeowner's policy is adequate to cover the contents in case of loss. Invest in a home security system. Get to know your neighbors - maybe even become "gasp!" friends with them! Have a trusted friend watch your house, water your plants, and feed your pets.
Above all, document everything you consider "valuable". Keep your receipts (I have boxes of receipts dating back over 10 years). For your really valuable stuff (cash, jewelry, guns, etc) - consider a personal safe, or a safety deposit box (a small size safety deposit box runs about $100.00 a year depending on the bank - it is worth every penny, depending on what you have to put in it).
Yes, this is boring; no, it isn't "sexy", and it doesn't involve using an Arduino anywhere. It is, though, what is called "common sense" and "being an adult" (17 year olds and under need not apply).
One other final bit of advice: keep a low profile and look "poor"; don't go all flashy on things, shop a lot at goodwill, purchase as many items used as possible (especially cars). Bank your savings. You'll end up with a good nest egg, and people won't ask to borrow money off of you. People will avoid hitting the beater you drive because it looks like you don't have insurance (the bigger and uglier the beater, the better - this doesn't mean it has to run poorly, though - learn to fix and tune your own car).
On the other hand, if this is just some fancy "do it to do it" project, then - carry on...
/yeah, I know - I'm such a downer...