recording room voice while phone is on-hook

Hi, is there a way
where we can record the voices in the room where the phone is placed, even if
the phone is on-hook ? like a spying feature, while using the microphone of the
phone ?

Given the right configuration and security credentials, it is possible to send a command to a phone to cause it to either automatically place an outbound call to a particular number, or start sending an audio RTP stream to a particular IP:port.  If the phone is idle/onhook, then typically this call/stream would activate the speakerphone/mic.

Note that the phone display and button lights do change to reflect that a call/stream is in progress, so it is in no way 'secret.'

The IP Phone Services SDK provides this capability: Cisco IPPS

Please see the 'CiscoIPPhoneExecute' request and the 'Internal URI Features' sections on 'Multimedia URIs' and 'Telephony URIs'

Thanks for your reply,

I just searched about Multimedia URIs, and read about the RTPTx URI,

my question is when using this URI, does the phone activates the microphone directly and send the RTP stream?
And what will be displayed on the phone in this case?

Yes, making the API request will cause the phone to start capturing audio and sending an RTP.  Depending on which audio path is active, that is normally the speakerphone mic for an idle phone.  If a headset was connected and the headset audio path selected, then that would be the mic used.

The visual appearance depends on the phone model, but could include the 'Speakerphone' button lighting up and an icon/animated-icon on the LCD display to indicate streaming.

If you really want secret, you should go full James Bond.  Here are two approaches (I like the first one, which masquerades as a power strip, but it's a GSM device with European power connectors, so it would stick out like a sore thumb here in the states).  Or you could just hide a baby monitor somewhere.

By the way, if you're in the states (and maybe this applies outside, as well), you need to know what the laws are for recording conversations. In some states, it is illegal to record conversations without consent of the recorded, and in some states, it's legal (but I think that assumes you're at one end of the conversation, not just an invisible listener).