Low DC Current (~ 1.2 A) SPDT for Arduino

No, it won't work when Vdd is 0V, the MOSFETs need a bias voltage to keep them open.

As Olin says it would help to know exactly what you are trying to do to determine the best solution, but for an electronic normally closed switch, here is a simple idea:

Most MOSFETs are enhancement mode, which means the MOSFET is off with 0V gate-source bias (Vgs) and turns on with a positive Vgs bias (for a N-ch, opposite for a P-ch)
What you need in this situation is a depletion mode device, which means with 0Vgs, the FET is on, and turns off with a negative Vgs (assuming N-ch again)

A typical JFET is a depletion mode device, and you can also get hold of depletion mode MOSFETs such as the BSS139.
So using something like the above, here is a simple circuit (that could be elaborated on if necessary):

Ignore the resistor R3, this is just to simulate a switch by setting it from low to very high impedance - the SWITCH node would be connected to your bias voltage needed to turn the FET off (so it's connected to -10V in this example)

Simulation:

Above we can see the SIG_OUT when the JFET gate is left floating (Red trace) and then when biased with -10V (Blue trace)
The signal in is 200mV pk-pk with a DC offset of 0V, so this can be used for dual polarity signals. Depending on the JFET used, the gate does not have to be biased so low, the smaller the Vgs required to turn it fully off the better.
Note that the ON resistance of this switch will be quite high, so you cannot load it too much - if you need to drive something then you will need a buffer in between.

If you don't want to use a negative rail, the same concept can be applied to a P-ch JFET:

I haven't included the simulation as it's exactly the same as above. The bias voltage used was floating (e.g. if using a switch on the gate it's open) and +10V to turn off (so switch would be wired to +10V)

The FET part numbers shown can obviously be changed if desired, I'm sure there are better parts out there - they were just picked from the small selection LTSpice has.

For the chip itself:

Datasheet says Basic Isolation: 354VDC/Vpeak; Reinforced Isolation: 184VDC/Vpeak.

Vpeak = 1.41(ish)*VAC = 338.4V. For Basic Isolation, it should be okay, though with saws and what-nots there might be spikes that are multiples of Vpeak and then you get in dangerous waters. It might still do, but I'd say, add an extra optocoupler to any communication going out and keep your measurement-arduino safe from human hands at all times.

((

EDIT:

Note how on page 2 where I got those numbers it also admits that the 2.1kVrms rating given is completely useless "Allegro does not test that, we just had that tested by UL a couple of times" -- Marketing at its best: Always read the small print!

End of Edit

))

For the board:

HELL NO!

Looking at the picture I see a clearance of near to none on almost all of the designs out there. They are downright stupidly designed. I am somewhat doubtful if it'd be smart to put a current above 10A through most of them, but probably because of the presence of the contact block you'll get away with it.

But I have not seen a design in the offerings with more than 0.5mm clearance between the measured voltage and the local signal ground. That is, by any standard, a factor 4 to 8 too small to work with 240VAC safely.

For info: Clearance is the distance between two copper traces and even in the oldest standards I have worked with the minimum was 2mm for European/Aussie mains and it certainly hasn't gone down after more research into several phenomena.