What is the ruling on swearing to divorce one's wife with three pronouncements (talaq) that she will not touch or operate a computer, and what are the implications of this in different scenarios?

If you made your wife's divorce contingent on her touching or operating your private device, then she is irrevocably divorced with a major, irreversible divorce [ṭalāq thalāth bainūnah kubrā] as soon as she does so. This is the view of the majority of jurists. To avoid divorce, your wife must completely refrain from touching the device.

Sheikh al-Islam Ibn Taymiyyah and Ibn al-Qayyim are of the view that a contingent divorce depends on the intention of the one who made it contingent. If he intended a threat and not to effect a divorce, then he is only required to offer an expiation for an oath [kaffārat yamīn]. They also hold that three divorces pronounced with a single utterance count as one divorce.

If you made the divorce contingent on an action by someone else (a wife or otherwise), and that person did what the divorce was contingent upon out of forgetfulness, then the Shafi'is are of the view that the divorce does not occur.

Buying a computer for her does not effect a divorce, nor does selling your private device to her effect a divorce if she touches it, provided your intention when you made the oath was limited to preventing her from touching your device as long as you owned it. However, if your intention at the time of the oath was that she should never touch the device, regardless of who owns it, then the divorce occurs if she touches it, even if it has become her property. If you had no specific intention, then one reverts to the reason for the oath.