Low cost C-Meter with good accuracy

What you need for a C-Meter: 
one AT89LP213/..214/..216/..2052/..4052, some additional elements, (one crystal) and around 300Bytes Assembler Software.

This idea is a low cost solution with good accuracy and linearity and could be used in several applications with capacitive and resistive elements.
We would like to sell this idea to interested customer. Sorry for those readers who would like to see schematics and more. 

We have a prototype available that displays the results of measured capacities on a LCD Display. Some features of that design:

• power on self calibration
• autorange from 0pf to 1µF with +-2pf resolution (up to 50nF)
• 1pF to 100pf with 1 pf resolution
• 300 to 800 Bytes assembler Software
• this idea is ideal for battery based applications
• measuring should be power supply voltage independence 
  (accuracy currently not tested at different voltages)
  
• this idea is working with nearly all microcontrollers

  Any input or questions are  welcome: Mail j.hulzebosch@gms2000.de