Keyboard in the Cockpit?
Allen, I don't know if you've spent any time in an RV cockpit before, but real estate is definitely at a premium, especially with all of the other goodies which are becoming available. I for one would not purchase a device which requires use of a keyboard while airborne. It's OK on the ground for doing firmware and software upgrades, but while flying? No way. Ditto for a dedicated LCD screen.
All things electronic in the cockpit are moving towards integration with a central controller (usually combines EFIS, engine monitor, moving map, weather display, etc. - BTW most have RS-232 capability). Devices which interface with this central controller have a definite advantage in my book. Think about it - the EFIS already has a small and eficient data input device appropriate for in-flight use, and a large, sunlight readable screen. Devices which duplicate this data input / display functionality and which serve no other purpose just take up valuable space IMHO. Devices which can serve double duty, triple duty, etc. are the way things are moving. There are other benefits too. If you eliminated the LCD and keyboad inputs, you could make the device smaller, lighter, and cheaper which might sell more units. CO Guardian's product is a good example. Their CO sensors plug into the EFIS and give you warnings (verbal, aural, and optical, if you want) of carbon monoxide levels in the cockpit.
I see the ideal APRS transciever as being fully controlled through the EFIS, and having the transceiver being remotely mounted. At most I might want a couple of LEDs on the panel for power status, transmit status, and the like. And as far as painting airborne APRS targets on the GPS, that's great. Even better would be front and center on the EFIS screen, in large scale, with declutter capability just like every other kind of data presented such as lightning strikes, NEXRAD, airspace, roads, rivers, waypoints, and NAVAIDS. A dedicated APRS screen or window might show incoming text messages (along with a unique "bing-bong" sound, or a sexy female voice saying "incoming APRS message, Mr. Studly Pilot Guy"
and allow a space for outgoing message composition "We've got some headwinds, and expect to be there a half hour late". This would represent a nicely integrated product with today (tomorrow's) avionics systems. But hey, that's just me!