On the local apps main ( dash board display window) With the status tab selected so you can see temperatures. Along side temperature numeric readings perhaps you could have a small fan graphic or even just a colored dot that showed up orange (when the internal fans come on) and then perhaps red (when the turbo fan comes on)
I know after some experimenting hanging around my classics as they warmed up. I worked out the temperatures that each fan kicks in at (48c) for the internal fans , then off again when its back down to (45c). From memory the turbo fan was (58c) then off again at (55c) Though the visual would quickly give you a idea of what fans are running.
Just an idea anyhow.