I haven't messed about with things like encryption, while using splashtop, so I don't know anything about it. But Splashtop (and I assume all remote desktop apps) makes you put in a password before you can connect to the pc remotly.
The password can be around 20 letters/numbers long too, so if you have a good password, like random letters and numbers, instead of your pet's name. You should be pretty secure. (I'd make it at least 10 letters/numbers long)
Don't no one go trying to hack my pc just to prove me wrong now!
I'v just been browsing my router settings, and I actually do have some encryption, but it's under the wireless network settings. Does that count for people accessing my pc remotly? (the pc is connected to the router with a LAN cable).