This is a game I thought of.
You have a kitchen and the aim is to protect your food from being stolen by your friends. In the kitchen will be assorted foods such as chocolate bars ,milk,bread or other items.
When your food gets stolen it sets off a timer of 15 minutes and to defend it you have to answer a question or enter a captcha within the time frame. If the food was a sponsored item maybe you need to answer a question about a website or something.
There might be a central "supermarket" where you can stock your kitchen from which has foods with different points attached to them. Rarer items have more points. You earn points based on how long you managed to defend your kitchen for during the past 24 hours. You might also have a message system so people can leave you notes when they steal your stuff
. "Im in your kitchen stealing your foodz!"
Maybe people could hire alarms or guards for bitcoins as an in game purchase for when they need to sleep
You could extend this to different rooms in the house such as the lounge room. Defending items you might find commonly in any longe room such as a tv,playstation,xbox,laptop etc...
I think you get the idea