For an example of legislation that modifies the common law on search of electronically stored information, see my comments on Vu. That legislation, which I blush to admit is New Zealand's, seems to authorise a search of a cell phone in circumstances which include where a person can be searched without warrant, not merely where there are reasonable grounds to believe relevant information will be found, and not on the lesser threshold of reasonable grounds to suspect, but simply on the basis that the information "may" be found.
I do not think that Riley justifies a reading-down of statutory powers of warrantless search in New Zealand. The express power in s 88 of the Search and Surveillance Act 2012, coupled with the elaboration of the powers in relation to places and vehicles in s 110 and persons in s 125 are not stated to be only exercisable if it is impracticable to obtain a warrant. But the overarching requirement of s 21 of the New Zealand Bill of Rights Act 1990 is one of reasonableness, implicitly both as to the decision to exercise the power of warrantless search and to the manner of carrying out the search. An issue of reasonableness will be a case-specific inquiry. It would be wrong to say that a warrantless search of a cell phone or a computer that was in the possession of an arrested person will always be unreasonable.