Speaking of smart ecosystem, the primary thing that comes to my mind is smartbulbs and smart speakers... Follwing are the IoT devices that i was interestd to see in market and that are truly innovative
A smartbulb emitting light that could be chosen from the smartphones
And a smart bt speaker ( much like amazon alexa)
A fitness tracker ( like fitbit) that stay charged fr atleast a month
A smartwatch that provides an easy way of receiving notifications and as well a atyle quotient...
A smart tv with an ecosystem of apps and services( how wonderful it would b to do the shopping right with your family, in front of the tv and stream movies directly into ur tv without all those wire and pendrive mess)
And when u make a smartphone try to make it as compatible and a converging centre of all the datas recieved from the smartdevices..