I spent the summer and fall jamming on RFduino for my OpenBCI products. www.openbci.com
Really like working with the modules! In order to get the high data rates and bandwidth that we require, we are using two radio modules running RFduinoGZLL. The Device is on our product (OpenBCI 8bit & OpenBCI 32bit boards), and the Host is on our USB dongle. I designed the dongle to be pin-compatible with RFduino shields, and it's really sweet with the PCB-integrated USB plug.
We are using the RFduino Host/Device pair as a serial pass thru to communicate to a target uC (either ATmega with UNO bootloader, or PIC32 with chipKIT bootloader). The serial link needs to be able to pass control characters and data, as well as work with avrdude to program the target uC. In order to do that, I added a switch to route the DTR pin from FTDI chip to either the dongle mounted RFduino module, or the GPIO6 of the RFduino. This allows me to program the RFduino on the dongle (switch with RFduino reset selected) or communicate and program the target uC (switch with GPIO6 selected).
I posted here over the summer about programming Arduino over RFduinohttp://forum.rfduino.com/index.php?topic=749.msg2384#msg2384
Anyway, you can see images of the hardware on our product page,https://openbci.myshopify.com/
And here's a view of the schematics, board-layout, and gerber fileshttp://docs.openbci.com/hardware/01-OpenBCI_Hardware#openbci-hardware-documentation-openbci-dongle