For sending outbound data, Spacebridge probably doesn’t offer much of an advantage to you. Its more for pushing data down to the device for remote access or remote control purposes.
You can try our cloud endpoint though. It was designed to be fairly lightweight for cellular use and if you’re using our hardware it’s built in to the SDK. TLS is supported as an option. https://www.hologram.io/references/embedded-apis
Otherwise, many people are totally fine using MQTT and things like that. You can do some tests and see how much data you end up using.