You've linked two icons that, generally speaking, refer to the signal strength of specific technologies.
The "connection speed" icon is typically used for WIFI connections. Take a look at the results of a Google Image search for "wifi icon." You'll see a similarity in the semiotics used.
The "bars" icons is typically used for mobile networks. Performing a Google Image search for "mobile signal strength icon" you will see a pattern in those semiotics.
If your "stand alone application" is showing an indication of WIFI signal strength, use the former. If your application is showing signal strength for mobile networks, use the latter.
Over time, users have developed an expectation of meaning associated with these icons. If you show the "wifi icon" users will interpret that as "wifi connection strength." If you use "bars" users will interpret that to mean "mobile network connection strenght." If you are aiming to show some aggregate signal or perhaps a bandwidth indicator a-la streaming video, then I caution against using either of the mentioned icons. Instead, use a meter of some kind (Like Netflix, Vudu, Amazon Instant, etc).