"Handbook of Fluidic Sensors" provides a list of fluidic sensors that were commercially available and their capabilities.
Fluid flow and pressure
a pitot probe is a simple example of how fluid flow speed may be sensed
Sound. For fluidics, you can more or less directly sense fluid flow and sound. All you need for a microphone is an acoustic horn to collect the sound. Fluidic circuits based on jet deflection amplifiers basically work off of acoustic signals. Although with traditional fluidic circuits it's difficult to operate at ultrasonic frequencies. Some fluid jets display sensitivity to ultrasound and ultrasound operated fluid switches have been developed. It's been proposed that such devices could be used to make ultrasound remotely controlled toys. Although the performance of this type of ultrasound fluidic switch is a bit dubious for this application in practice.
Although it's difficult to operate at ultrasonic frequencies with fluidics, fluidic proximity sensors based on using ultrasound to transition a jet of fluid to turbulent have been employed commercially. See page 109 of the handbook for more details.
Although the above sensor provides only a boolean response. There are also fluidic devices which can modulate and demodulate ultrasound, meaning you could potentially make a workable sonar range finder despite not having switching elements which work at ultrasonic frequencies. Although this has never been done before and one might have to push the boundaries of what's possible with fluidics to do this. It might become more practical if we run fluidic devices off of low density gases like hydrogen and helium, which have higher speeds of sound and can thus enable higher operating frequencies. You can also measure short distances by measuring back flow from a jet and other fluid dynamic effects, see page 19 and 57 from the handbook above.
Touch Sensors/limit switches
One way to make a simple touch touch sensor is make something that opens a valve or hole when bumped. There are numerous examples of this in the handbook above. Another way is to have an open hole which we blow air out of with a another channel leading back to the circuitry we want to drive. When the holes open, the output is zero, when the hole's covered, the air gets redirected to the channel. This type of device is typically called a back pressure switch and is shown below.
This same technique can be used to measure short distance too by looking at the back pressure.
One can make a simple analog of an optical encoder by using a jet of fluid instead of a beam of light. One can also use a channel that changes width so that the fluidic resistance changes with rotation, enabling analog absolute encoders to be made
Strain Gauges/force sensors
One way strain gauges have been made is to have a pipe with a helical channel in it, sort of like a spring, and put rubber tubing in the channel. Compressing the pipe compresses the tubing and increases the resistance to fluid flow
When fluids heat up their viscosity, density, and speed of sound can change, which we may sense with fluidic circuits. Fluidic capillary pyrometers, which measure temperature by taking advantage of the fact gases become less viscous at higher temperatures thus decreasing the resistance of a capillary tube, have been used to measure the temperature of molten steel. Another means of measuring temperature is to take advantage of the fact that a fluidic oscillator will change in pitch as the temperature changes due to the change in the speed of sound.
fluid viscosity, density, and speed of sound can also change with composition. A simple example of this is that we can sense the amount of helium/hydrogen in the air with an oscillator. The higher the pitch is, the more helium/hydrogen there is in the air. Fluidics has also been used to make a non-electric gas chromatograph
Purely fluidic gyroscopes have been made. Rotation can cause a fluid to swirl and form a vortex increasing fluidic resistance.
These have been used in an aircraft autopilot and have also been used to stabilize missiles and rockets. One can also take advantage of the fact that a jet of fluid will deflect due to rotation or acceleration(see page 7). These have been used to make fluidic tank gun stabilization systems. It's also interesting to note that the first in car navigation system was based around this principle, although the jet was sensed electrically through hot wire anemometers
Most fluidic amplifiers are based on deflecting a jet between to ports using perpendicular fluid flows. Instead of a perpendicular fluid flow we can put a magnet on a flexible beam in the jet, so when there's a magnetic field the flexing of the beam will deflect the jet.
Light's the most difficult thing to sense. In general it's difficult to transduce light to mechanical signals as the energy light carries tends to be low. Unless of course the light is bright. Fluidic sun sensors have been made, where we use a lens to focus sunlight on two curvy pipes painted black. Because fluid decreases in viscosity with temperature, we can look at the difference in resistance between the two pipes to figure out where the sun is. A one axis fluidic attitude control system capable of tracking the sun intended for a solar probe was demonstrated using this approach. A similiar approach has been proposed for making IR seeking railgun launched projectiles.(Fluidics can withstand the enormous EMP) Another means light can be sensed is using the photoacoustic effect. If the light is flashing on and off very fast, it will cause a cavity of air to expand and contract making sound. While this sound may be very minute, we can use fluidic amplifiers to amplify it into something we can work with. The non-electric gas chromatograph mentioned above was able to amplify the photoacoustic signal from a 1 mW led into a pneumatic control signal. Continuing the trend of absolutely bonkers applications of fluidics for the SDI, a fluidic ICBM interceptor control system was demonstrated that used a laser to control divert jets. One proposed means of sensing light with fluidics of doubtful practicality, but potentially higher sensitivity than the thermal approaches used above is to use a chemical reaction that is triggered photochemically. For example, we have a continuous stream of hydrogen and chlorine directed into a chamber upon exposure to sufficiently bright UV or blue light, the hydrogen and chlorine will react explosively. We can then sense the pressure and flow of the explosion. Perhaps a strip of light sensitive explosive could be used. In short, it will be difficult to sense anything except bright light.