It seems like they used 100mW IR explicitly so they could use the platform outdoors. In most cases, you're fine looking at the reflected (usually diffuse) light

It seems like they used 100mW IR explicitly so they could use the platform outdoors. In most cases, you're fine looking at the reflected (usually diffuse) light, but you shouldn't stare into the beam. If you're working indoors you should be fine with visible low-power lasers, e.g. 1mW red or green. There are numbers in the paper (linked in the article) and they explicitly calculate the power vs the safe threshold. They basically say you shouldn't go closer than 1.5m to the device in operation. They give some suggestions to improving that, but it doesn't look like any of them were actually implemented.