Zimmerman, 28, of Sanford, Fla., made an unexpected appearance on the witness stand during the lengthy hearing. He has admitted shooting Martin, an unarmed black 17-year-old, but says he acted in self-defense.
"I wanted to say I am sorry for the loss of your son," Zimmerman said. "I did not know how old he was. I thought he was a little bit younger than I am. And I did not know if he was armed or not."
Circuit Judge Kenneth Lester set bond for Zimmerman at $150,000. He ordered Zimmerman to be under Global Positioning System monitoring.
Zimmerman, however, was not expected to be released Friday.
Florida prosecutor Bernie de la Rionda argued Zimmerman shot a young man who was "minding his own business" and argued for either a high bail or no release. Zimmerman's lawyer, Mark O'Mara, asked bail be set at $15,000, pointing out his client surrendered as soon as he knew he had been charged.
Martin's parents were in the courtroom, The Miami Herald said. Zimmerman's testified by telephone, with his mother saying they had been threatened.
A petition brought by several news organizations challenging the sealing of normally open court records also was to be heard Friday.
Zimmerman, whose father is white and mother is Hispanic, told police he shot the unarmed black teen in self-defense.
The prosecution alleges in a public filing Zimmerman "profiled" Martin and "falsely assumed" he was "a criminal" -- one of the "punks" who "did not belong in the gated community."
If convicted, Zimmerman faces a maximum life-in-prison sentence.