This case only seems to cover devices the suspect doesn't already willingly carry.
Cell phone records are not the papers or effects of the person being investigated, they belong to the cell phone company. The Supreme Court "consistently has held that a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties."(442 US 735,743-744)[1] That quote is from the Court's ruling in a case that was specifically about police getting a record of telephone calls that a suspect made, Smith v. Maryland, 442 U.S. 735 (1979)[2].
Congress laid out rules for police obtaining such records in the Electronic Communications Privacy Act (ECPA) of 1986[3]. The ECPA doesn't specifically mention cell phone location information (since this was 1986), but it does include "name; address; local and long distance telephone connection records, or records of session times and durations; length of service (including start date) and types of service utilized; telephone or instrument number or other subscriber number or identity, including any temporarily assigned network address; and means and source of payment for such service (including any credit card or bank account number)."
A court order may be issued under section 2703(d) of the ECPA[4] "only if the governmental entity offers specific and articulable facts showing that there are reasonable grounds to believe that … the records or other information sought, are relevant and material to an ongoing criminal investigation."
This is a lower standard than for a search warrant. A warrant requires "probable cause", that is "information sufficient to warrant a prudent person's belief that … evidence of a crime or contraband would be found in a search".
[1] http://supreme.justia.com/us/442/735/case.html#743
[2] http://en.wikipedia.org/wiki/Smith_v._Maryland
[3] http://en.wikipedia.org/wiki/Electronic_Communications_Priva...
[4] http://www.gpo.gov/fdsys/pkg/USCODE-2010-title18/html/USCODE...