You're approaching this from the wrong angle. You want the file upload to occur within the API in which your app works. Usually (always?) you have to use a aspx/php/other script to accomplish this.
Flex (say...) will present a dialogue box to the user to select the file, then Flex calls an aspx script to move that file from the users computer onto the server temp folder, then returns that (temp/random) path back to the Flex app - which in turn can call a geoProc, passing it the file.
The geoproc can then parse the NMEA sentences (or whatever data you have, CSV, etc) and [do whatever] to write it into SQL/ESRI FC.
I would start by looking up:
1 Your native API and a sample upload file code snippet (they are rampant) eg http://weblog.cahlan.com/2006/09/uploading-files-with-flex-and-php.html
2 A script (aspx or php) to fetch the file. eg http://www.w3schools.com/php/php_file_upload.asp
*1 actually contains a sample for the entire process, but I threw #2 in there for more context.
3 Then write a geoproc (or php still!!) to write to your SQL. (php if you are not writing into an ESRI GDB - for certain! I think this is required actually... Flex can't talk to SQL, if I'm not mistaken - or I've just never done it...)
I find this chained method to be very easy to follow, debug, and customize (control).
Best of luck!
Apologies: I totally missed the EDIT on the end... If your users are local, I would just get python to parse the file line by line and write to SQL directly. No GP Tool, no AGS required. I am missing something?
You are specifying that the map should be loaded with the "hybrid" map type (in your l_Options object), which is is one of the available map services hosted at services.arcgisonline.com/ArcGIS/rest/services.
In order to remove the dependency on ESRI services, you should not specify a basemap, and instead load your own layers from your own instance of ArcGIS Server.
Best Answer
There is a good one here: https://github.com/DavidSpriggs/ConfigurableViewerJSAPI.
Click here to View Live app. Includes:
Another one is in another answer, Esri CIS did a great work developing such an application. Pity it is in Russian.
Most of other apps I've seen tend to be more ArcGIS Online specific: here you can find some of the templates (some are really good and would cover most of the needs).
Esri has also released a bunch of JS apps with some viewer-like functionality which you could reuse for building own viewer with perhaps a more complete functionality set. These apps can be found at ArcGIS for Local Government resource center. Very many of them have a live version to play with and include simple geocode search function, basemap gallery, and print.