The small wireless calypso costs $249 and has a 67% worse threshold than the $79 entry level Kestrel (1 m/s vs 0.6), and similar accuracy spec (3%), half the operating range (60mph vs 134 though that doesn't really matter for rocketry), impossible to hand-hold, and is not standalone, requiring a bluetooth device to read it out. I don't see how it's superior to an impeller unit for most people except that the sensor part is smaller and more robust mechanically, and it reads out the direction. It doesn't meet any of the use cases that center around pulling it out of your pocket for a quick reading in a few seconds. If you look at the data sheet it's obvious that their target market for that unit is in cruise/race sailing. The wired units start at $399 and are intended to be used as adjunct wind sensors for fixed and portable weather stations.