This morning, i checked Apple AppStore and saw that the app has been approved by Apple and now available in their store. I downloaded it on my iPad and start testing it. You can find the online documentation by following this page : http://hub.libreoffice.org/iosremote or use the step by step tutorial on the app itself.
The easiest way to connect is by using the same WIFi network on both devices. Start impress and select Slide Show > Impress Remote. Next start your Impress Remote and start searching for your computer (i tested on my desktop). Try to pair and enter the number showed on your computer on your device and you are now connected. You can start give your presentations using your iPad or iPhone or iPod Touch.
Here's an example of it's UI: