Quoted By:
A 4yo is going to have both limited interest and limited attention, so it's important to give her something that is both highly visual and immediately gratifying. I think LEGOs (or the larger blocks, if her fine motor skills aren't there yet) would be perfect. Not only do they allow her to express and develop her creativity (debatably one of the more important aspects of technology aptitude), it will give you plenty of time to spend with her. Once she's up to about 7 or 8 years old, you can get a simplistic electronics kit and build things with her. Kids love things that buzz and whir, and at ~7-8yo she might be able to hold her attention to it long enough to figure out what is actually happening with the electronics.
Another good idea would be an old smartphone/ipod touch that you aren't using. Load it up with some fun apps, and help her learn to use a piece of technology in a fun and transparent way.