The reality is, you don't need to panic. There are solutions and they generally don't cost that much.
I've done some basic research and have come up with some solutions. The one you pick, is entirely up to you and your budget. There are a lot of options, so don't assume this is an all inclusive list.
If you are unable to use either hand
The best option is to use voice input. There are some devices out there that use facial muscles and brain waves, but they are generally best for gaming and require a lot of setup/time to get useable. I guess it would be possible, but very labor intensive.
Dragon Naturally Speaking is probably one of the best programs out there. Not only does it allow you to type, it lets you control the entire computer via voice commands. It does take some training so the software recognizes your voice, but I've seen it in action and it is great. It is available for both Windows and Mac. The nice thing, for users of Scivener, is that it works really well (according to a writer that I follow on Twitter...wish I could remember their name!). It does have some issues with people who are not Native English speaking and using it to control/write in English. I expect this will improve as the technology improves.
Cost: $99 (for home edition)
Pros: Easy to use, Training is minimal, Cross Platform
Cons: Issues using in English if not a Native speaker
If you have one hand available
In addition to using dragon, there are several options available.
One handed keyboards
Their are a lot of one handed input devices out there. The one that is probably the most common is something called a Frog Pad. These devices allow you to type using only one hand. It does take some training to get used to the keys, but it keeps everything within a small area and gives you a full keyboard with only a handful keys. I've heard people can get some pretty high WPMs using it.
The biggest issue at the moment is that it is only available as software for the Mac/iPad. There used to be a physical device for the PC, but the new model won't be out until 2013. I can't tell if it will be PC compatible. Looks like it might just be for Mac. They do have software for the PC that costs $24.99 and they'll ship you the clings to put over the keys to convert it to one-hand.
Cost: $129 (includes software and Mac Magic Pad cover)
Pros: New Model will be USB and bluetooth compatible. Company has an app for iPad that will convert the iPad keyboard to a FrogPad
Cons: Seems to be only available for Mac users. Some mention of PC version, but I couldn't tell. New model won't be available until 2013.
As I said earlier, there are other one-handed keyboards out there and even some prototypes that have some interesting capabilities. If you are looking for a one handed keyboard, just do a Google search. They aren't necessarily that cheap.
Another solution is the Ergodex DX1 Input system. With this, you can literally put a key anywhere on the pad, configure it via the software on your computer and make yourself a truly unique keyboard layout.
Pros: Can make a completely custom keyboard layout. Windows/Mac compatible.
Cons: Setup can be a bit time consuming as you have to configure each key.
Another solution, presented to me by Marieke Nijkamp, is the use of a tablet. In her case she bought an Asus EEE Transformer Prime. She indicated that she was able to use Swype and the normal keyboard layout one-handed. I'm guessing this would be true of any tablet device (Windows, Android or iPad). For an extra fee, you can get office production software and then import the text into a larger computer for later editing.
Pros: Lightweight. Swype and alternate soft keyboards available for one handed use. Can copy files back and forth with DropBox or Google drive.
Cons: Most tablets don't have writing software on them out of the box. Windows based tablets can have Office installed, but cost more. iPad and Android tablets have apps available for a fee.
As you can see, there are options. All this data was pulled up with a simple search and a couple conversations on twitter.
Just remember, there are solutions. Don't panic. All is not lost.
Hope this helps. Remember, this is just a starting point for more research.
Do you know of any other solutions? Have you used any of the options I've suggested? If so, leave a comment. I would love to hear more.
'Till Next time.