Years ago, Epe Online www.epemag.com published a project "Micro picscope" a simple visual signal monitor.
It shows a representation of the signal waveform using an alfanumeric 16*2 lcd display.
Here a PBP version with PIC16F690

Obviously the performance are very limited; i consider this project a toy.
A graphic area of 8*40 pixels is inadequate to show anything with an acceptable accuracy.
The bandwidth is limited to 4-5KHz
The frequency counter is limited to 6 digit, the precision depends by the internal oscillator frequency.
Despite that, i like it.
Have fun!

Regards
Gianni