I don't think you can setup alarms with the Octo, but you can do it with the Aquaero 6LT.

Alarms give you the possibility to make a sound or shut down the computer.

And the 6LT has a passthough RPM cable to connect to the CPU header of the mobo. So you're mobo can also do the shutdown incase the flowmeter stops spinning. But I'm not sure how this works on the Octo

Have a look at the manual:

12.1. Signal output configuration
The signal header can be configured as a speed signal output or as a switching
output.
Option “Power switch (53216)”: This mode can be used for emergency shutdown
of the PC, if the “signal” header is connected to the power switch header of the
motherboard using a suitable cable (art. 53216). Before connecting the cable,
make sure the signal output is configured correctly! After connecting the cable, test
the setup by deliberately creating an alarm condition. If the PC is not shut down,
the cable header connected to the motherboard must be rotated by 180 degrees
and the test has to be repeated. Emergency shutdown may result in data loss as
operating system and running programs are not shut down properly!

12.2. Alarm reporting and alarm limits
Select the data sources to be monitored and set appropriate alarm limits. If the
current reading is below the limit (flow sensors) or higher than the limit (temperature
sensors), an alarm will be raised if the check box “Activate alarm evaluation”
is set for this value.
On the alarm page within the aquasuite, all sources that currently raise an alarm
are highlighted with a red background color. Alarms that have been active at least
once since device start-up, but are not active presently, are highlighted with a yellow
background color.
Make sure only to use readings for alarm evaluation that are functional with your
specific setup.

Although the alarm function is good, I can't see a way to evaluate software sensors or activate media keys for the OCTO. It was possible to press the software power button with the Aquaero if the CPU or GPU got too hot, and games would halt, the computer would attempt a software shutdown and the alarm would sound. I can't see a way to do that with the OCTO.

You can set up alarms for the on-board hardware sensors, flow and fans only. There also doesn't appear to be a buzzer.

The OCTO has only some simple alarm options. It's not an high end fan controller like the aquaero. If you need the functions you can go ahead with an aquaero LT and add the OCTO conencted via aquabus.