How can I use my phone or tablet as mousepad?

I just set up my Ubuntu desktop to use our living room TV as a monitor, and I would like to be able to use either my iPhone or Nexus 7 tablet as a mousepad/keyboard for controlling it from the couch. With Mac/Windows there were plenty of apps that did this, what do I need to do this using Ubuntu? And just to be clear I am NOT looking for a Remote Desktop on my phone/tablet, I want to use them as a mouse and keyboard. Thanks!

I use remotedroid. You just need to install the client on your tablet, and then connect to the local IP of your running server. It sends mouse movements, left and right click and typing. The server doesn't even need installation, is a simple .jar archive. To run it:

java -jar /path/to/RemoteDroidServer.jar

Here you can download the server (the client is in the market):

http://www.remotedroid.net/

There is another option that I use which is GSConnect extension (Basically KDE Connect with better stablity on gnome). It has a lot of other features also as a bonus. You need KDE Connect on your android mobile / tablet also.