The Seeed Studio DS Nano v3 oscilloscope is a pocket sized scope at a pocket money price. Its bright 2.8in. TFT LCD has a resolution of 320 x 240 to display analogue signals with frequencies up to 200kHz. With a sampling rate of 1Msamples per second it has a 12-bit resolution (4096 levels) for analogue signals up to 80V peak-to-peak and it can store the waveforms in its 2Mbyte of on-board storage. And the stored waveforms can be replayed or transferred to your PC via USB too. There's a wealth of trigger modes and automatic measurements including edge triggering (rising and falling), frequency and duty cycle measurement and more. Power is supplied by its internal rechargeable battery and recharging is through its mini-USB port which is also used to load software updates.
It has a useful built-in signal generator that outputs a square wave from 10Hz to 1MHz.
Seeed Studio publish a handy user manual for the DSO Nano.