I have used this app on a number of occasions with great success.

However, I want to know whether the app places my bid in real time via my phone. That is, does my phone need access to be online to place the bid in say the last few seconds before the bid or is the simple fact of me placing the snipe the day before enough?

Once you set your snipe, you don't need to be online for the snipe to actually work.

Thank you