This is not digital but when I first saw it I was so convinced that it was that I contacted TiSPLAY  to find out more about their range of products.
The T-Board is a static A3 media platform that is illuminated through activation. Its maker TiSPLAY are, I suppose more in the standard outdoor/ambient media sector – their aim to provide out of home advertising opportunities to local businesses (though they are missing a big opportunity I feel if they do not also chase national sales brands).
I am told that with a little R&D the T-Board may go digital over the next 18 months or so.
TiSPLAY basically secure the rights to install and advertise on the T-Boards within high profile car parks throughout the UK, currently …
- At-Bristol – Bristol
- Beechwood Shopping Centre – Cheltenham
- Chinatown – Birmingham
- Arcadian Centre – Birmingham
With the following going live 1st quarter 2008
- Kingsland Shopping Centre – Dalston, London
- Observatory Shopping Centre – Slough
- Queensmere Shopping Centre – Slough
- Charing Cross – Glasgow
- Cambridge Street – Glasgow
- Cadogon Square – Glasgow
- Emerygate Shopping Centre – Chippenham
Their business is obviously focused around Car Parks but nevertheless it is a neat solution and a well thought through product (and business for that matter).
The attached PDF (just under 1MB) shows the T-Board in a variety of real life scenarios and uses