This app lets you donate wish list items to homeless people you pass every day

Marcellus has lived on the streets of Philadelphia for more than four years, and he wants you to know that being homeless isn't easy.

"It's, like, waking up hungry. Going to sleep hungry," he says in a new video, as he fiddles with a small piece of blue plastic in his hands. "But this right here — this got me some food. This got me clothes. This got me a shower and all that."

It's not just any piece of plastic. Marcellus is holding a Bluetooth-connected beacon — a small component of an app called StreetChange that could transform how passersby help curb homelessness in their cities.