Your heart is in the right place, but my experience with those $10-20 dongles is that they are good for strong signal reception, such as my local public safety trunked system, but they just can't cut it in the real world as an all-around receiver. Software can only do so much with crap hardware.
I tried to set up one on a linux laptop that I was running at my parent's house to receive the local baseball games broadcast on an FM station about 15 miles away. It wasn't happening. Not sensitive enough and getting overload from the many other FM transmitters nearby. No big deal, but if I were serious about that project I would have to upgrade the SDR hardware to something over $100 to do something useful and at that point I might as well scrounge up an old AM/FM radio pulled from a car like a broadcast engineer I know did.
I'd love to find or build a small but powerful SDR to perfect a modern scanner. Uniden locks you into their design choices. SDR# is still a bit too geeky for general use. If it had a good UI with user selectable operating parameters instead of being stuck with a limiting set that would be a win. Usability is key to general acceptance. That's what this DMR portable offers I suspect.