From your linked definition of iridescence:

> **Iridescence** [is] the property of certain surfaces that appear to change color as the angle of view or the angle of illumination changes.

Thus, the following node setup should suffice:

![Iridescence node setup][1]

The setup simply takes the dot product of the view vector and the surface normal and maps it to a spectrum. If you're not familiar with vector math, you can basically think of a dot product as a measure of how orthogonal (perpendicular) two vectors are; the dot product of two (normalized) perpendicular vectors is 1, while the dot product of two parallel (or anti-parallel) vectors is 0.

You can put this node group in any shader and get a nice result. I tried it in a Diffuse BSDF, but putting it in a Glass BSDF might yield some nice bubble renders.

Here's an image of Suzanne wearing her iridescent cloak (the factor is set to 1.0 to exaggerate the effect):

![Iridescence on Suzanne head, fac=1.0][2]

Here's the factor turned down to 40% (lower works in better lighting setups, but my sky texture is blowing it out):

![Iridescence on Suzanne head, fac=0.4][3]


  [1]: https://i.sstatic.net/WrBu9.png
  [2]: https://i.sstatic.net/v4WiQ.png
  [3]: https://i.sstatic.net/O6RDK.png