Viewing Busy Extensions on Cisco SPA504G

Hi,
I was hoping there was a way to setup the Cisco SPA504G so it would act like a landline system in that it would appear to show “active lines”. For instance, we have one office that is hard to see when someone is on the phone, and we don’t like to send people to their voicemail. Their extension is 104. I’d like it to show on our other phones when x.104 is using their phone. Is this possible? I may have been naive in thinking since the phone had 4 line buttons that each button would appear to stay active during any given call.
*EDIT
So it appears that this may be possible, but Ooma hasn’t implemented it yet? When I try to go into the phone configuration settings I am not allowed to access the administrator settings on the phone to setup a monitored extension. I assume that is because Oooma has already done this setup and doesn’t want users to be tweaking things? It would be really great if we could make this happen . I would only need to map 2 of the phone’s line buttons to two extensions to show me when they are on the phone.
*EDIT
I should also probably mention that currently we only have one SPA504G. The other 3 phones are analog. I am wondering if we had all IP Phones if it would display these extensions differently or no? Right now the display on the one SPA504G is x101 for all 4 buttons.
*EDIT
The feature I am talking about appears to be available on Vonage. They call it the Busy Lamp Field (BLF). Any chance we can enable this on Ooma IP phones? LInk to the Vonage feature: http://businesssupport.vonage.com/app/answers/detail/a_id/21418/~/busy-lamp-field-(blf)