Glad you replied. I did a little digging for giggles. I don't know if you're up for a little light coding but I found Gnome-contacts. It's a pretty lightweight contact management app. It's available in the Debian repo for the CHIP. It is too big for the PocketCHIP screen, but the interface is clean and simple and (to me) looks like it can be scaled down.
The source is available. It's written in Vala a C# like language. Changing the UI elements shouldn't take a lot of coding skill. And the app is pretty small so understanding it shouldn't be too horrible.
I found another contact app 'address-book-app' This is for Mint, so it's even lighter, and has an simple attractive interface (Windows 10ish). But I haven't gotten it to save a contact.
On the calendar front, less good news. There is a Gnome calendar app but it seems pretty simplistic, and for some reason is not yet in Debian Jessie mainstream yet, just in development builds.
If you have another linux box it's probably worth installing Gnome-contacts and giving it a look.