Crystal Display Systems in the UK has started to sell ‘transparent LED Glass’ Displays for daylight and shop window applications. The LEDs are in a custom subframe and are available in a number of pitches (5 x 8, 7.5 x 8, 10mm) and with 2,500 cd/m² or 6,500 cd/m². Transparency is claimed at 68% up to better than 80%, and outdoor versions are available.
The company has a (pretty poor) video online.