One issue is remotely logging into the OBiTALK portal to access your OBi's settings. Just doing that doesn't give anyone access to your home IP network or to the security panel directly. Either disable OBiTALK portal access entirely, or assign a very strong password (at least 14 characters, using a combination of upper and lower case letters, numerals and punctuation symbols). Even if someone were to guess your password, they'd also have to be an OBi expert, which I doubt any criminals would be, to further manipulate your settings.
In theory, someone would need to know how to use the OBi auto-attendant, and/or change your OBi's settings to re-route telephone calls in via the auto-attendant (which you can also disable), and then know that you have a security panel, and know how to access it. Unless you are a character in a Mission Impossible or James Bond movie, that is extremely unlikely.
If you are that concerned about security, consider that the vast number of intrusions are physically via unlocked or easy-to-force open doors or windows, or forced entry smash and grab. Focusing on physical security is more important than any alarm system. It would be easier to just cut your internet and phone lines than to hack your OBi. If you are still not comfortable, then get a dedicated connection for your security system...POTS line, or cellular.