Has anyone built a PIC-based digital O-scope / logic analyzer ?

I have a rough idea as to how to proceed.  I would basically use an external
ram buffer, counter for the ram address, 8-bit a/d tied to the data bus of the
ram, and a programmable gain & offset op-amp to buffer the input to the a/d.

The only area I am unsure of is a good trigger / sync circuit to release
the clock for the address counter.

I would use a PIC to interface with the PC via RS232 to transfer the buffer
contents to the PC and to accept programming parameters from the PC.  The PIC
would be responsible for reseting the trigger / ram buffer circuts and
programing the offset & gain of the input amp.  The PIC would not be responsible
for clocking in samples because it would be too slow.  The address counter
would be clocked from a separate crystal.

I would like to keep this low-cost, otherwise I might as well go out and buy
a used scope!  I would like to keep total cost within the $100 range.

My purpose for this is to make a useable device for analyzing
signals and timing in future PIC projects.  I really don't need a high
precision instrument, just one that will let me adequately see what is going
on in my circuits.  I would like it to be useable in the 0-10Mhz range, so
I presume I would want to be able to take samples at up to ten times the
highest frequency to be observed.

I appreciate your feedback and suggestions.  I realize the I am asking for
a lot from a handful of cheap parts.. <G>

Thanks.

Dan