NOW FREE : I thank everyone for the support along the way. Now everyone can enjoy this application for free!

NFX Oscilloscope is a simple signal vs. amplitude analyser.

Currently there are two input options for the application.

***** USB SUPPORT ****** (only for android 3.1 and greater)
PLEASE ENSURE THE GABOTRONICS DEVICE IS UP TO DATE!!
The newest and best input option is a USB hardware device provided by Gabotronics. USB host mode has now been compatible since android 3.1, therefore most new phones and tablets will support USB host mode (Please check device). NFX Oscilloscope supports the Gabotronics Xprotolab/Xminilab, this has 2 analogue input channels and 8 digital channels and measures a tiny 2.5 x 4 cm!! The device it's self is a cheap portable alternative to most mainstream oscilloscopes, and has many different features. Connecting the Xprotolab to the NFX Oscilloscope provides a powerful and cheap oscilloscope platform for your portable needs. For more information on the Xprotolab or Xminilab click the following links.
http://www.gabotronics.com/development-boards/xmega-xprotolab.htm
http://www.gabotronics.com/development-boards/xmega-xminilab.htm

So match this application with the cheap device from gabotronics and you will get a great portable oscilloscope!
Note: Only the analogue channels, logic Channels and tone generator is supported on the xprotolab/xminilab/xprotolab plain

Spec list for xprotolab:
2 Analog Inputs
Maximum Sampling rate: 2MSPS
Analog Bandwidth: 200kHz
Resolution: 8bits
Input Impedance: 1MΩ
Buffer size per channel: 256
Input Voltage Range: -14V to +20V

Currently the USB mode has been tested on Samsung Galaxy Nexus , Asus Transformer , Asus Nexus 7 , Samsung Galaxy S3
There has been problems reported with android version 4.3 and USB host, there is a major bug in the release, which is set to be updated at some point in the future.

Please note : Most devices will need a OTG cable to enable usb host mode. See phone specific instructions for more information.

***** Microphone SUPPORT ******
The second option is the microphone input to the android device. This can be used to attach a scope lead to the jack socket. More information can be found at the following website.
http://www.instructables.com/id/A-Preamplifier-for-Smartphone-Oscilloscopes/
Features include, triggering for different impulse and continuous signals. In addition to this there is level measurement and fundamental frequency readings

It is possible to control the amplitude, time/div and trigger level whilst monitoring. Settings included trigger directions, sample rates and voltage span calibration.

Have a look at this blog for more scope cable information from a fellow user of Nfx oscilloscope.
http://www.instructables.com/id/A-Preamplifier-for-Smartphone-Oscilloscopes/

If you are unhappy in anyway with this product, feel free to contact me and I will help all I can, if I cannot help I will offer a refund at any time (even past the 15 minute google refund mark)