Oath Lenses act to make someone desire to fulfill a particular promise they make, with the strength of the desire growing as the person ignores it longer and longer. They send a keyword signal when installed, to verify that they have been activated properly. There are many services on Infosphere that sell Oath Lenses and verify their use. They are designed to be nearly impossible to remove or bypass, including interfering with the use of any Lens that would modify the possessor's memory or beliefs. Many have failsafes that allow them to be removed in case of extreme duress, or in cases in which the oath becomes impossible to fulfill.
One useful side-effect of an Oath Lens is an ability to resist post-Mesh-Hacking influence. Even a successful mesh-hacker will have extraordinary difficulty removing the Lens (roll of 150+ on Cognitech & Programming), and they will be unable to alter the wearer's memory or beliefs until they do.
Tech Levels: Cognitech 5
Cost: public domain