Butter. It has to be kept cold and hard, yet it's easiest to use when it's warm and soft. Many a slice of fresh bread or toast has fallen victim to this fact. Texas-based inventor Doug Foreman, however, decided to do something about it. His biēm device is loaded with a stick of cold butter, and delivers it onto food in spray form.
biēm uses regular third-party butter sticks, and simply heats the top layer to 95 ºF (35º C) as needed. That melted butter is then shot out of the spray nozzle at the touch of a button, using no aerosols or other chemical propellants. The rest of the stick is left solid, and can simply be put back in the fridge along with the device.
The spray is reportedly cool to the touch. Along with its application to things like toast, popcorn or boiled veggies, it could also be used in the place of non-stick oil sprays on frying pans.

An accelerometer in the device detects when it has been picked up, and automatically turns it on. Its integrated lithium battery takes 30 minutes to fully charge, and should be good for 5 to 6 sticks of butter if used continuously, or about a week of use by a family of four.
Washing it pretty much just involves running it with soapy water in it, while it's put into a higher-temperature "cleaning" mode. It is not dishwasher-safe.
If you're interested in getting a biēm, it's currently the subject of a Kickstarter campaign. A pledge of US$129 will get you one, assuming all goes according to plans. It can be seen in use, in the video below.
Sources: biēm, Kickstarter