There are many small companies which provide anything from staff augmentation(engineers for hire) to full product design services(come to us with an idea and a bag of money and we'll make it happen). I'm in San Diego and know a couple companies that do this:

http://www.serranosystems.com/

https://fairwaytech.com/

http://www.a2etechnologies.com/

http://www.jetheaddev.com/