Drawdio with fx.
Actually Drawdio's are just 555 timers, which are cheaper than PICs. And the circuit is open source. So please make your own with leftover or cheap parts, and please don't buy them unless you need to (better to make from scratch). They are not based on capacitance but on resistance, which is doable on a PIC but challenging to get the right effect.
Let me know if you have any more questions about how it works, or google drawdio.