If there were cheap tablets available to use as an extra screen, then all of us wouldn't buy extra units for mapping or sonar. I don't see the major companies allowing it to happen. They will keep the processors in the head units to make us buy more.
Agree.. unfortunate. technology-wise, it's relatively old and very doable. but, they won't do it as you said. they will make you buy second unit instead.
I found this from other forum, looks like this model supports video out. People who is shopping might consider this option.
"hummingbird 1100 series has video out where you can just plug a cheapass monitor into it and be done"