Our friends and family sure are wonderful aren't they? They encourage us and make us feel better even if we we're doing something dumb. For getting feedback on our ideas, this is terrible.
To avoid the problem of getting less than honest feedback, pitch your ideas as someone else's. Rather than saying "I had an idea for an app that does X," say "So I saw this new app today and it does X." Their response will give you a better indicator of how they may react to it if they didn't know you.
Of course, this doesn't mean that their honest suggestions are the best ones all the time. Plenty of people have advised against great ideas. And of course you should probably claim ownership of your idea when it counts (like in a meeting at work). But hopefully this can help you get a better sense of how strangers would react.
Photo by Robert McGoldrick.