I am a fan of such devices. I own a DSO203 (2ana+2dig channel pocket DSO) which works well till about 2MHz and is suitable for my kind of work with PIC and other microcontrollers. I cannot do any analog / accuracy needed type things with it, but allows me to scope signals for shape and amplitude. It too has a signal generator built in. You may argue, that it is a toy. Yes, indeed! However, the convenience is unbeatable when you can carry your DSO in your pocket. Another speciality of this scope is that it is FOSS. I have contributed to the source code in a small way. Multiple versions of the firmware are online and you can choose which one suits your taste.

Another mid-range between pocket and desktop scope I own is the JDS2022A from jinhan. This runs 20MHz analog bandwidth. However, it is a power hog as it uses relays for selections.

This budget 3-in-1 scope looks very tempting except they don't ship to India anymore. Else, I would certainly buy this as another tool in my cupboard.

Counter argument would be - with so many PC scopes available, why would anyone buy such a device. Well, you cannot beat the convenience of having a self-contained DSO with battery power for one.

Anyway, thanks for asking this question. Got me interested in this.