Even the most obscure ideas have plenty of competitors (I know I write table planning software for events). If you come up with something that has no competitors, either:
-you didn't look hard enough
-you are a genius who spotted an untapped demand (very unlikely)
-no-one wants it (very likely)
Also, remember that the main competitor to a lot of software is Excel and post-it notes.
That said, the more competitors the harder it is to get noticed. Ideally pick something where you have got a reasonable chance of getting on page 1 or 2 of Google.
-you didn't look hard enough
-you are a genius who spotted an untapped demand (very unlikely)
-no-one wants it (very likely)
Also, remember that the main competitor to a lot of software is Excel and post-it notes.
That said, the more competitors the harder it is to get noticed. Ideally pick something where you have got a reasonable chance of getting on page 1 or 2 of Google.