I'm not a lawyer nor do I pretend to be one so I can tell you is that this a very simple and basic task for an Uno which has six analog inputs that can resolve 10 bit accuracy (0 to 1023 counts). The inputs are zero to approximately 5 volts full scale. I say approximately because in order to save costs, there is no precision 5 volt reference, the board uses the on-board 5 volt regulator, the same voltage that powers the entire Uno board. That's not great for precision voltage measurements but it's more than adequate for most Uno projects.
You can use an analog input to create the alarms. You might want to use a filtered analog value, which can be easily done in software. It depends on what you find when you connect the transducer to the Uno and see what the analog readings look like from a stability standpoint. Hydraulics can create some rather "spiky" pressures, especially as solenoid valves open and close.
You'll also want some hysteresis (or deadband) in the switching points so the LEDs don't flicker close to the switching points.
You can drive standard LED's directly from a digital output pin so long as you have an appropriate value current limiting resistor in series with the LED. Digital output pins should be limited to a maximum current of 20 milliamps which is more than enough for modern, bright LED's.
Relays will need a driver circuit, usually a transistor although it is far easier to purchase relay driver boards that include the driver circuits and you simply connect digital outputs directly to board, apply the rated voltage and you're off to the races.