With cost-saving voice over Internet telephony taking off and replacing wired phones, makers of cellular phones are taking notice. Cell phone heavyweights Qualcomm, Texas Instruments, Nortel Networks and others are incorporating VoIP into the cell phones, chips and wireless network equipment they manufacture or design. VoIP is the basis for Internet phone services, popularized by commercial VoIP provider Vonage and free peer-to-peer phone service provider Skype.