Is there a way to connect a GPS to ArcGIS via USB? At the moment the GPS extension only appears to support comm port connections. It would be good to know if a USB connection can be made, then perhaps my Android device can be connected and ArcGIS can use its GPS.
At the time of writing, the answer is no. To promote the idea, please upvote this on ArcGIS Ideas.
Your question is a rather loaded question. Firstly, there's the realm of USB GPS and quite a number exist and will work with ArcGIS, but, this is not what you're asking.
You're asking whether an Android phone will present itself as a USB GPS when connected to your PC. I would say that most Android devices on the market will utilize the USB port for other purposes and is very unlikely to share the location sensor through it. This would most likely require changes at the firmware level, i.e. from Google itself.
Instead, there are alternate options for Android.
There are a number of GPS sharing applications in the Android Market.
The typical scenario is they transmit GPS position data over Bluetooth from your Android unit in NMEA. Your PC will need be able to pair with the Bluetooth profile, usually serial port. Once paired, ArcGIS will believe you have a regular GPS connected at a regular serial port. These applications usually transmit GPS position data in the NMEA protocol simulated standard GPS devices on the market. You can try your luck with these. I do recommend TRY before you buy, because not all apps will work with all phones.
Also note that most phones have a consumer grade A-GPS where position data is generated via a number of clever algorithms (cell phone position, IP address position, WIFI location position) and, depending on your location, your position may be quite unreliable.
ESRI's solution is ArcPad. You can install the software on a compatible device and it allows you to check data in and out of a personal or a multiuser geodatabase.
For Garmin GPS the next best thing is the DNR Garmin application. I find the free stand-alone application much better then some plugins I had to pay for, such as the MxGPS for example. MxGP allowed me to interact with the Garmin device from inside ArcMap but it wasn't as full featured as the DNR Garmin. (unable to add fields, change and upload values, etc.) It was functional but too simple.
Having said that MxGPS now has a new (ArcGIS 10 compatible) version which I have not yet tried and it suppose to support all that it didn't in the past as well as geodatabases, COM (serial port), USB and USB Mass Storage Devices, even GPX so you could take a look at that option.
Lastly, the long awaited DNR Garmin is coming this month and beta is already available. The application is called DNRGPS and you can download it here. I have not yet personally tested this software so I cannot comment on the new functionality. Also, DNRGPS is now open source.
You can and have done in the past - with most GPS units including the Garmin product you can create a virtual com port.
Solution create a Virtual Comm port:
For example with any Garmin GPS unit you can use spanner software.
"Spanner allows you to use your GPS 18 USB with most NMEA 0183-compliant mapping programs. It adds a virtual com port interface to your GPS 18 so that you can send NMEA data to other programs. Spanner works only with GPS 18 software version 2.90 or later. Be sure to load the latest GPS 18 software before using this program. System Requirements - IBM-compatible PC running Windows XP operating system and an available USB port. WARNING: Windows Vista and Windows 7 are not supported"