A combination of two objects, a z-sensor mount bracket for an 18 mm capacitive or inductive sensor and a 40 mm cooling fan shroud to direct cool air onto the print.  These are for use with a Sintron Prusa i3 MK8 Extruder, but could easily be modified to fit other printers.

The instructions for hooking up the sensor are typically on the side of the sensor itself or in its data sheet. Also be aware that sensors like this come in two flavors PNP and NPN. An overview of what I used also be found here: http://www.instructables.com/id/Enable-Auto-Leveling-for-your-3D-Printer-Marlin-Fi/

Also it depends I suppose on which controller electronics you use.

For a Ramps 1.4, which is what my printer has:

Regarding the second fan (and in my case the extruder cooling fan) - it is controlled via the Fan output on the Ramps 1.4 which is D9. D9 is controlled using the G-Code M106/M107 commands in the Marlin or Repetier firmware. This would not be the case if you are using a second extruder heater.

I'm actually not sure how to the hookup in case of a second extruder and its heater. Potentially I guess a person could use 12VDC relays or high power SCRs to turn on both of the extruder heaters together using the D10 output.

One other note of warning, I recently modified this mount to move the sensor to be behind the x-carriage and thus be closer to the center of travel for the x-y plane. Otherwise the sensor winds up hanging over open space when the heat bed was homed on the y-axis, That meant I had to be super careful about the homing order and could never to a HOME ALL command a second time if the sensor was not over the heat bed.

To deal with the above problem of homing, I just posted the new z-axis proximity sensor mount for attaching using screws (two spaced horizontally at 25mm apart) to the back of the x-carriage. Its not a perfect solution either. But it does provide a safer homing order using XYZ instead of XZY.