How is usage billed with the Hologram cards…here in Australia with M2MOne each session has a minimum 1kB usage charge, even if you are only sending a few bytes.
There are no minimums or charges per connection. If you connect 999 times a month and use 1-byte of data per connection (including all overhead!) you will be charged for 999 bytes. Now as I mentioned about overhead this is impossible as there is always overhead.