I've had a logic analyzer project in a notebook for a few years now.

It's basically an FPGA hooked up to some memory with either a bank of comparators as inputs or just right into the FPGA. (The comparators allow one to set the logic thresholds and it keeps you from blowing up FPGA inputs with errant high voltages.)

It talks to the host computer over USB.

The FPGA design is really something that can be done as a senior design project.

The PC software? That's what kills me every time.

-a