I am not an inventor but if I were, this is a product that I think could be a great assist in our current lifestyles.
From the beginning of all our lives, we have grown up with a telephone. And as the mobile phone became an integrated part of mobile lives ( Steve Jobs enhanced the mobile experience to make it extraordinary ), the home phone has all but been made the step child of our phone use.
With that said, I still have a land line. Many are doing away with their land lines in lieu of their mobile phone. Now lets go back about 4 decades when the princess extension phone was all the rage. The reason? Because it provided the convenience of being able to speak on the phone in the room you were in.
When you charge your cell phone, it is very likely it is not where you are when it rings.
That brings me to a product I would like to see invented. Extension phones for the cellphone. I envision a cradle for charging the phone that has phone extensions. In fact like the land line, as many extensions as you want. You simply plug in the cell phone extension phones and voila, you can answer your cell phone in any room you might be in. When you take the cell phone out the cradle, the system just goes to sleep so as not to interfere in the voice mail messages when you can't answer it. It may even be possible to have messages sync in both locations.
This is a small thing but something I have thought about and hopefully someone will work out the technology and soon we will be able to have cell extensions and be able to do away with the need to have land lines and the duplication of phone service.