Head-operated computer accessibility tools (CATs) are useful solutions for the ones with complete head control; but when it comes to people with only reduced head control, computer access becomes a very challenging task since the users depend on a single head-gesture like a head nod or a head tilt to interact with a computer. It is obvious that any new interaction technique based on a single head-gesture will play an important role to develop better CATs to enhance the users' self-sufficiency and the quality of life. Therefore, we proposed two novel interaction techniques namely HeadCam and HeadGyro within this study. In a nutshell, both interaction techniques are based on our software switch approach and can serve like traditional switches by recognizing head movements via a standard camera or a gyroscope sensor of a smartphone to translate them into virtual switch presses. A usability study with 36 participants (18 motor-impaired, 18 able-bodied) was also conducted to collect both objective and subjective evaluation data in this study. While HeadGyro software switch exhibited slightly higher performance than HeadCam for each objective evaluation metrics, HeadCam was rated better in subjective evaluation. All participants agreed that the proposed interaction techniques are promising solutions for computer access task.