Has anyone tried one of these?

Too cheap to be any good?

Universal 15000rpm Motorcycle LCD Digital Speedometer Tachometer Odometer Gauge

Nope.......But my goodness they are cheap...They look remarkably similar to the Koso RX2n. If it's the same item just rebranded then they must be ok....

Just watch the seller I bought a wireless module for arduino from them, had to open a dispute against them as they didn't sent the item came up with the excuse we didn't send it with a tracking number but checked with the post office and they delayed it. I wonder how they were able to find out this and if you look at the feedback it seem quite common for them.they then sent the bit and it turned up eventually. They were not to happy to receive negative feedback don't know why.

Yes, they work pretty good except the tachometer. It seems to be looking for a sine wave crossing 0v, when hooked up to my cam position sensor (1 tooth so reads 1/2 rpm) it worked well.