One of the most frustrating things for me is that there aren't any really good "official" solutions for wireless controllers on two of my favorite classic systems - the Dreamcast and Saturn.
The Saturn has a few options including a set of official Infrared controllers that were released by Sega of Japan and Sega Europe, as well as a few 3rd party brands:




The offical ones are usually quite expensive (especially the black ones, which have gone on eBay recently for upwards of $200) or in poor shape (yellowing on the Japanese models). Also, those who own them can vouch for their outdated IR technology giving generally bad accuracy and short range.
The 3rd party controllers from UFO and Nyko I haven't tried. But the asking price is pretty high at ~$90. The UFO ones advertise to be infrared, so I can't image they're better than the Sega ones. If anyone owns either of those, feel free to chime in.
I've only ever seen this set for the Dreamcast. They aren't that common; again if anyone can contribute a review for these then feel free. I'm pretty sure they are IR as well given the translucent cap where the beam would be.

So, what to do? Well, you could build your own, but short of that we'll have to turn to some alternatives.
STEP ONE:
First off, you'll need the Logitech Cordless Precision Controller for the Playstation 2. These go on eBay and Amazon for about $15 to $20 a piece, which isn't bad. The problem is that they are often mislabeled or pictured as the Cordless ACTION Controller, which has some thumbstick and trigger problems with the Dreamcast. There's a comparison below. I own a few of both types, and the ones that are in good condition are quite excellent controllers. The buttons are responsive and D-Pad is average. They are generally considered to be the best wireless controllers for the Playstation 2, and with one you can have wireless control on the PS2, PSX (with a controller extension so the memory card can fit above the receiver), Saturn, and Dreamcast. Not bad. Better yet, there doesn't seem to be much input lag on any of these systems even with converters, but I'm not a huge expert on this subject so fair warning.
Cordless Precision (buy this one):

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Cordless Action (not this one):

STEP TWO:
Next you'll need a DragonCast Super Converter, made. These feature full VMU support and are one of the few PS2-DC converters that support the Logitech Cordless Precision. Bingo! This converter maps the thumbstick, D-pad, face buttons, and triggers of the Cordless Precision to the Dreamcast pretty well. When you hook up your Cordless Precision, remember to press its MODE button to turn on the analog feature. Because the Dreamcast also has four face buttons and two triggers, this is a surprisingly good mapping!

STEP THREE:
For the Saturn you'll need a bit more elusive piece of hardware: the Tototek Classic Joypad Converter. Tomy at Tototek hasn't given it a production run in a while, although if you make your voice heard on the forums that would be great. Still, there are a precious, precious few on eBay at the moment and they seem to pop up there about once every other month. This is not as elegant a solution, either, since the Saturn has six face buttons and two triggers. Here's how it maps:
- A, B, and C to Square, Cross, Circle
- X, Y, and Z to Triangle, L1, R1
- L and R to L2, R2
Although the notes say otherwise, it seems to only work when analog mode on the Cordless Precision is turned off. Either way, the analog mapping would only map the thumbstick to the D-Pad, so this won't replace your Nights 3D controller. Still, I'm happy with it and think it's a great solution.

OUTTRO:
All this kit will cost you about $60, far less than it would cost to buy any of the controllers I posted at the beginning, and with far less effort than modding your own set! Entrepreneurs out there should note that there is probably a big market for this! The Cordless Precision is a good controller, but it's only an acceptable match for the Saturn and having truly 2.4gHz official Sega Saturn wireless controllers would be pretty amazing.
Anyway, hope this guide helped some of you looking for a way to ditch the cords in your living room!