The requirement is technically "easy" [tm].
It's "just a matter of doing it".
Making it compact and pretty may be harder :-).
"All" you need is a display with the resolution, size, weight, brightness and power consumption that you require and a lensing system to reduce the viewing distance to what is acceptable relative to your eye. A mirror or prism may be used to change direction by 90 degrees or some other angle.
Superb example of what can be achieved can be viewed (literally) in any of the SONY DSLR cameras which have OLED EVF displays instead of an optical viewfinder. The Sony A77 camera with XGA (1027 x 768) electronic viewfinder has perhaps the best example but there are others with lesser resolution
Excellent A77 EVF review
A77 eyepoint to lens is 27mm - which shows you what can be achieved.
A much cheaper way to start is to obtain some cheap +4 diopter reading glasses
($2 / pair here - YMMV), take out the lenses and look at your display with 1, 2, 3, 4, ... stacked together.
1 x +4 diopter lens gives you a ~= 1/4 = 0.25 metre = 250 mm viewing distance.
2 x +4 diopter lenses stacked (in close contact) gives you
8 diopter = 1/8 m focusing distance = 125 mm viewing distance.
3 gives you ~= 83 mm
4 gives you ~= 60 mm or about 2.4 inches.
...
Or stacking lower diopter lenses or a mixed set may give you better results.
Putting on several pairs of spectacles at once and looking at a book gives you some idea of what to expect. Quite reasonable quality can be achieved with cheap lenses. If you get serious enough you can get N diopter lenses ground to your specification.
