Similar to this question but I'd like to know about 3rd Party/aftermarket options instead please.
I've heard about motor multiplexers and the like but are there others, i.e. more sensitive colour detectors etc.?
There are MANY companies that offer third party stuff for NXT:
... and I'm pretty sure I forget several!
There's lots of third party SENSORS to attach (see very helpful list from Philo), but I found it hard to find any info on third party MOTORS to connect to EV3. Pretty much only the mindsensors.com extensions to connect RC servos and position encoding adapters to slap on power function lego motors. So I took to the LEGO hardware documentation and put together a small info page on how to connect a small third-party DC motor (sensored) to control it from the EV3 brick. It's all here: http://www.biasedlogic.com/index.php/running-third-party-motor-with-your-mindstorms-ev3-nxt/ comments and feedback welcome
In short: the EV3 can power a dc motor up to about 500mA (full load) directly, provided the motor is equipped with a 5V-compatible encoder (many cheap motors are available with magnetic/Hall effect encoder wheels). It does not have to be an optical encoder like the original LEGO motors have, a simple magnetic wheel with hall sensors can do just as good a job.
In addition to these helpful answers, I'd like to add that the reason there are so many 3rd party devices and options is because the NXT supports an incredibly wide variety of electronic and data protocols.
The NXT can directly interact with sensors over:
- Bluetooth SPP
- RS-485 (only on Port 4)
So pretty much any robotics/hobbyist device that uses one of these methods can be interfaced with the NXT. See the NXT Hardware Developer Kit for technical details and specifications. Note that in order to use many of these devices you'll have to use a 3rd-party firmware solution as well, such as NXC or LeJOS.