If I use only my phone and not my computer can I still get all updates and any other communications from Microsoft tru my phone? the health app on my computer seems useless
I'd say it is "relatively" useless - its stated purpose is to sync your data and nothing else. Therefor, if you install it just to sync data (as is its purpose) it's not useless. Most people look at the data on their device, which syncs data as well - making the desktop app redundant for them.