Yukari owns cellphones... or at least "cellphone-type thingies". It's confirmed in Subteranean Animism. However, I think she uses her boundary powers to operate the cellphones. I mean, how else would she be able to hook them up to Reimu's yin yang orbs?
From her Impershable Night prologue, she also owns a television set, but she uses it as a spirit container box, whatever the hell that means (Perfect Memento indicates this is a popular use for television sets in Gensokyo)
Apparently, she can hook up her television set to allow you to see what's going on through Reimu's yin yang orbs, too.
...sorry, I digress. It's Reimu's stage 1 conversation with Suika in SA
http://touhou.wikia.com/wiki/Subterranean_Animism:_Reimu_and_Suika%27s_ScenarioSuika: (Oh, hey, you can hear me.
We can talk using your yin-yang orbs.)
(Yukari set them up!)
(and later)
Suika: (...I've got this TV and this
cell phone-type thing Yukari came by with)
(... so, uh, what's a cell phone?)
(Yukari also set up Alice's dolls in SA, so apparently Yukari can hook cell phones and televisions up to dolls, too)
Under normal non-modified-boundary conditions, cell phones don't work in Gensokyo
http://touhou.wikia.com/wiki/Perfect_Memento:_Encyclopedia:_Outsider"They immediately put the tool called "mobile phone" to their ears, and after that they are at a loss of what to do next.
"
"Is this since the tool emitted sinister sounds?"