ちょっと = a little/small いいですか? = alright?/ok? You can use "ちょっといいですか?", when you are asking someone to spend a little time for you. For instance, if you ask a question to someone, that person will spend some time to answer you. So you are making sure if you can ask something by saying "ちょっといいですか?", in advance. It is like saying, "Can I ask you something?" or "Do you have some spare time?"

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打扰一下 会話ではこんな感じに使います。 「すみません、ちょっといいですか？」「はい、なんですか？」「日本語の質問があります。」

strongly agree with Poisonous Apple:-) In addition, when someone ask you, "ちょっといいですか？" while you look obviously free, it may imply that he or she wants to talk with you in person (not in public) by changing the place to have some private conversations. Also you can use the phrase when you want to speak to (or get an attention of) a person who is doing something, talking with someone else, reading, etc... In this case, it is the same as "May I interrupt you?" In a closer relationship, you may use "ちょっといい？" or only "ちょっと・・・"