Do yourself a favor and dont go the SAFC route, and I'm speaking from experience as I am also a DSM-er. The closest option you have to get standalone capabilities for piggyback pricing and similar style of operation as DSM link is Nistune or Calumsult. Both are almost exactly the same as DSM link in the sense that you pretty much chip a stock ECU and then are able to tune/datalog in real time using a laptop.
An SAFC used is like $150 possibly over $300 for a new SAFC NEO as you can no longer buy SAFCIIs brand new unless they are old stock. I payed $365 plus shipping to get it there for Calumsult and he covered the return shipping. So for under $400 I was able to get my stock ecu chipped and part of his service includes a base tune for your setup and a usb cable that connects your ECU to your laptop.
Then you use any variety of open source tuning programs including Tuner Pro and Tuner Pro R/T (I use them) or you can use Nistune software with a calum board etc. However nistune costs more then Calum, both for software and hardware. Either way you get similar performance from both, calum being the more affordable route.
Hope this helps a bit here are some links, if you need further help or clarification contact me directly.
Calum:
What is Consult? FAQ - SR20 Forum
Tunerpro:
TunerPro and TunerPro RT - Professional Automobile Tuning Software
Nistune:
NIStune - Nissan Realtime ECU tuning
