USB Oscilloscope

[Labarum]

I have seen USB Oscilloscopes for as little as £20. Are they any good?

[Techno Commander]

Depends what you want to do. They are marginally better than an I phone app.
If you want a "rough idea" of your amps frequency response, then they are reasonably accurate.

If you need to measure micro volts of distortion in a digital circuit, then maybe you need to look elsewhere.