Still seems to be quite a lot of confusion on what you can and can't do with weatherlink.com data views. Let me try to summarise:
There are 3 ways of viewing wl.com data online:
1. Standard web browser, which like any other HTML-type page viewer allows viewing on any device running a regular browser whether that's PC/Windows, Mac, smartphone, tablet etc (though smaller smartphones obviously aren't ideal because there's less screen real estate).
CURRENT weather conditions can be viewed FOR FREE via the Bulletin screen for ANY (non-private) station with data updates every minute (or at the plan interval for cellular stations, ie Connect or EM).
HISTORIC data charting etc requires a PRO account (ca $50pa), which also adds several other features.
2. WEATHERLINK smartphone app which provides access to similar CURRENT weather conditions and 1-minute updates as the browser views and again is FREE.
3. MOBILIZE smartphone app which requires a PRO plan and provides access to extra features like forecast temperatures, rainfall etc, basic charting and several others including CDD/HDD/GDD etc.
There are only 3 levels of plan in common use: FREE, PRO and PRO+. If you want access to historic data online and other Pro features then you need the Pro plan. The Pro plan provides access to all Pro features, ie there is only one Pro plan type that covers all contexts.
And, if it needs spelling out, any number of viewing devices have simultaneous access to the free features - there is no per-device limitation. Actually, the same also applies to the Pro features, except of course you must have access to a wl.com account whether the weather station has been upgraded to Pro level.
(NB Just a summary of the main features - there are all sorts of additional features like notifications, embeds etc etc some of which are available FREE and others requiring a PRO plan)