A material that can become very permissible to heat or not, depending on a dynamic configuration.

The first implementation is a block that would have many through holes, where thermal insulant or thermal conductive fluid would flow. The more conductive fluid flows, the more it would be permissible to heat. The other variant is a inflatable plastic pouch, where only insulant fluid would flow through. If you pass more fluid the pouch becomes thicker, and the material becomes more heat insulant.

One possible application of this is make house roofs permissible to heat in winter, but not on summer. That could help thermal comfort and save energy with air conditioners.

A material that could turn from insulant to conductor on-the-flight, that means during its operation. Semicondutors are like that but their nature is defined in the factory, during manufacturing. 

If you come to think about it, switches are like this, but they are approximated by hard 100% conductive or 100% insulant values. I'm proposing something that could go any value in-between.

In fairness, I coudn't come up with an application. It just sounds very cool.

Much of my reasoning seems to happen in making a physical property variable, in retrospect. You would be surprise how often that leads to actual applications.

This is like a large speaker, used for concerts, events or parties. 

It picks up with a microphone the sounds of the surroundings and plays those sounds amplified. The idea here is to have simple sound solutions that can be mounted quickly. If necessary, the speaker can have some filtering capabilities, for noise. 

This is a plane intended to fly both in atmosphere and in space. It changes shape from a perfect sphere in space to a plane-shaped craft in the atmosphere. Naturally the internal usable volume is fixed.

At the very least it would look neat in a sci-fy movie.

Space. This is a collection of ideas that are basically putting a translucent object between the Earth and the Sun, in order to filter out the radiation. 

Imagine a giant glass object, shaped as disk. The disk has propulsors and can move around like a vessel, or alternatively, is towed by a vessel. The idea is that it would position itself between Earth and the Sun, at some distance where the disk's size is small enough to be constructed. There, it would filter the sunrays. This could aid in preventing melanoma or fight global warming. 

In another variant, the disk would be actually a thin hollow glass tank, filled with a solution. We would change the concentrations on the solution to our needs.

This is radical geoengineering: the risks are enormous. It would affect every living thing on the planet. It is not something you would do casually.

A parallel currency that would be earned when someone does certifiable acts of good.

In honesty, I haven't worked that thought completely. The intention was to have something that encouraged cooperation between people.

This is another space idea. Imagine a barge that would have an orbit around the Sun and the Earth, very elliptical. When it got to the Sun, it would extend solar panels (possibly solar fabric) and charge itself with solar energy. It would need massive batteries, possibly with a higher energy density than we have available today. When it got back to Earth, it would charge space stations or even send energy directly to Earth wirelessly (somehow) or by landing the batteries.

An artificial body organ, biological or technological, to produce medications, vitamins, or supplements. 

This is a wild, naive idea. 

Could you submerse a turbine in a place where ocean currents are superficial and strong and tap into its energy?

I have many doubts about this because I know very little about these currents, how fast they, are, the depths, the distance from coast. The turbine would be supported by a floating platform, perhaps be anchored in the seabed if it is possible. It would require a transmission system to send the energy to mainland.

This was inspired by a calculation I did once that estimated the area of the oceans and seas, compared to landmasses. It is a lot of virtually useless space. We should increase, in my opinion, our presence on the waters. Many ideas follow this line.

If you have a particle stream, and from the origin of the particle stream you send a electromagnetic signal, does it reaches the target of the particle stream with a drop better than 1/r^2?

Here the particle stream can mean subatomic particles, or larger particles such as a sand-like material.

The motivation for this study is a way to transfer energy from orbit, say in orbital solar farms. It would be like a waterfall falling from orbit, that you would replenish from supply trips. The energy math (to send up, to receive) would need to be advantageous.

A variant of this this idea, with the same purpose, is if the sand-like material is actually tiny-bateries, dropped from orbit and collected on the ground. I don't know if there is a size or shape of particles that feels less with reentry.