An alternative is the 8x8 Grid-EYE from Panasonic, costs around £30. The Melexis equivalent is a 16x4 which costs about the same. Note you'll need to fill in a fairly lengthy export/release form to get hold of the Grid-EYE sensors. I haven't had any problems ordering them from Farnell, just tell them what your project is.

Both are fairly easy to talk to over I2C. You can make a passable wireless (low-res) thermal camera using something like a Particle Photon.

The MLX90640 isn't out until September unfortunately.

NB: Actually Farnell have the Grid-EYE for only £16, but the full range ( -20 to 100) model is backordered. You can still get the 0 to 80 version easily.