Have a gander at this: Nano-Filter
Here's a better picture of it:
I saw one of these units on display and set up on a betta bowl at my lfs. The betta looked very happy and not a spot of finrot on him anywhere so I imagine the parameters were held in check very well. This little thing seemed to keep the water absolutely clean without creating much current.
Oh yeah, did i mention the fact that this HOB filter is no more than than 3x3x2 inches max!!!! Seriously, this has to be the smallest HOB filter I have ever seen! By my accounts, This thing seems to be perfect for a 1 gallon set-up and looks to be as easy to clean as an Aquaclear.
So, do any of you have any experience with these units?