Subject + 监视 + (着) + Object
监视 (jiānshì) is a verb meaning "to monitor," "to surveil," or "to keep watch on." It implies close, often suspicious observation of someone or something. For example, 有人在监视着他 means "someone is watching him."
保安通过摄像头监视着停车场。
Bǎo'ān tōngguò shèxiàngtóu jiānshì zhe tíngchēchǎng.
The security guard monitors the parking lot through the cameras.
她总觉得有人在监视她的一举一动。
Tā zǒng juéde yǒu rén zài jiānshì tā de yījǔyīdòng.
She always feels that someone is watching her every move.
警方已经监视这个嫌疑人好几天了。
Jǐngfāng yǐjīng jiānshì zhège xiányírén hǎo jǐ tiān le.
The police have been monitoring this suspect for several days.