Real world? I'm still with my first lust: A stacked Maytag Neptune pair.
Fantasy world? Like Henene4's, my 2 are in my head.
They're for those of us who're stuck with 120v and no vent. It's a condenser dryer with a Peltier-type dehumidifier going at the same time. Instead of hook-ups for cold water and drainage, there'd be one tank you could fill with an ice bath and a larger tank to catch all the drainage. There'd be 2 sizes: one to match the typical 24" combo and one to match LG's latest 4.3 cu. ft. combo.
Target market would be people who have a combo washer/dryer. You do a FULL load in your combo, take half of it out and put it into my fantasy dryer. The combo will stay hooked up and run its usual drying cycle only half full. When you're done you just unplug my fantasy dryer and roll it into a closet or corner somewhere.
Matching it would be a simple drying closet. Tall and narrow, it'd have lots of folding racks and be heated by a small, oil-filled electric radiator at the bottom. It'd have just one control (a timer) and a thermal cut-out to prevent overheating. Fold up the racks to hang a few shirts. Unfold the racks for socks, underwear, etc.
Is this the most efficient way to do laundry? Of course not. Of course it'd be slow, but it'd be way better than a combo alone or going to the laundromat. I've been in my new building just a month. I realize it's too early to commit to buy here when my lease is up, but so far I love it and the ONLY negative is the "no washer" rule. That is supposedly in the process of being revised, which is great
I won't bore you all with the details, but I can't see either 240v OR venting as possibilities. Hence, my fantasy dryer.
Jim