SF has fixed the certificate issue. There was never a security issue with the site, only an expired certification. It has been renewed and all is well. Sorry for any frustration this has caused you :)
Both the iPhone/Apple and Android versions of the SF mobile app are now available for download from the resources page. The app is free for all members. It will allow you to get notifications on your mobile device whenever a thread or forum you watch has a new post, when your thread or posts get replies, when you recieve a private message, etc. Chat is not accessible on the app as it conflicts with the software on the site.
The links to download are in the resources area - https://www.suicideforum.com/community/resources/categories/example-category.1/