You will also need to use the command "set alg sip enable". You do not need to specify application though as you are using the standard SIP port (5060). Also, it's not as much opening the high ports as translating the IP address of the phone in the data portion of the invite packet.
Part of the invite tells the phones the IP addresses and ports of the endpoints. The SIP ALG will rewrite this private address to a public IP, as well as perform port translation if needed. Without the SIP ALG, the mobile phone will try to use 192.168.1.101 to connect to the SIP phone. As this address is unrouteable via the internet, the voice portion will fail. The SIP ALG will also handle opening the pinholes needed (random high ports) by parsing the invite information.