The perks of this application is that you can idle several accounts at once, and you do not need to have Steam installed on the PC you are running it on, which means you can rent a VPS and keep it running for weeks on end. This program acts like a stand-alone Steam client and will require you to enter your Steam account details. Neither applications require you to have the game you want to boost installed, but you do need to own the game in your library.
The two programs work differently - and depending on how you to idle, you may want to pick one over the other. HourBoostr and SingleBoostr are two applications developed to idle games on your Steam accounts.
