Changing parameters in Arduino without the IDE I’m installing Arduino-based well monitors in my local community.  Each well is different and has slightly different parameters and several hardware variations.  Currently, when I need to make a program change I have to uninstall the Arduino, bring it back to my computer, reprogram it, then reinstall it.  I’m developing these units as I go so there are various refinements that arise as well. I’d love to be able to reprogram a unit in place.  It seems like it could be done with another Arduino but I don’t currently have the skills for that.  The second, less flexible, method would be to use dip switches to select various options.  This option is attractive but would limit me to only the options that I know of at programming time.  Is there a third option I haven’t thought of?  Has anyone else tried programming one Arduino from the other?
Edit: I’m primarily using Unos but I’m working on a low power version that will use a Mini Pro. The units are accessible as far as USB cables and such. However I don’t own a laptop.
Sounds like you need a Standalone programmer. I offer one, it loads the target device from a program you select on SD card.  Up to 256 programs can be stored on 1 card. 
Check it out here  www.crossroadsfencing.com/BobuinoRev17/Programmer.html