A variety of technologies were used, according to The New York Times:
Observing from behind mirrored glass, C.I.A. officers used cameras with telephoto lenses and infrared imaging equipment to study the compound, and they used sensitive eavesdropping equipment to try to pick up voices from inside the house and to intercept cellphone calls. A satellite used radar to search for possible escape tunnels.
Despite the efforts, technology and millions of dollars used in the operation, agents were never able to photograph or record the voice of the man living on the top floor of the compound. According to the Times, agents called a man who took regular walks in the compound's courtyard "the pacer," but they were never able to confirm that he was bin Laden.
"You've got to give him credit for his tradecraft," a former senior CIA official who played a leading role in the manhunt told the Post.
On the other hand, the official said, bin Laden's decision to go to Abbottabad left him vulnerable. While it was not an obvious place to hide, and took him out of range of the U.S. drones that patrol the border with Afghanistan, Abbottabad is a place where "anybody can go."
"It makes it easier for the CIA to operate," the official said.
According to the Post, the safehouse was shut down after the raid.