Data collection from raspberry pi and send to computer (without using Ethernet or Wifi)

Question

I use the Pi as sensor data collector and would like to to transmit the data back to software that is installed on my computer (and probably the software will instruct the Pi to perform some tasks, e.g: clear data history, change date time)

For my application, due to some constraints, I am not allow to use Ethernet port as mode of communication/data transfer.

Any other choices I can use? I was thinking USB communication but seems both Pi and PC are USB HOST

I am ok to use either Model A, B+ or Compute Module

Updated 2 Apr 2015

1. The Pi is to be mounted with sensors (e.g: DS18S20 temperature sensor) and put inside the chassis of a desktop PC, collecting climate data (e.g: temperature, humidity)

2. The desktop PC has no networking interface (thus, wifi/wireless or Ethernet solutions on Pi is not preferred, favourable choices would be USB or serial)

3. A software on that PC will be automatic interfacing with the Pi to grab sensor data and Pi is to be able alerting the software if any sensor exceeding threshold (e.g: too humid or too hot)

Answer 1

An USB Null Modem Cable could work. It's for USB-host to another USB-host. Each end appear as a (fast) serial port to respective host.
http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_USBNMC.pdf

Answer 2

You can go for a Bluetooth connection. There are cheap BT dongles for your RPi out there (quick installation tutorial) and then use rfcomm to interact with your RPi.