Sonar is ASO keyword research and rank tracking built for indie iOS and Android developers. See real search volume and difficulty for every App Store and Google Play keyword — data from Apple and Google, not estimates — then track your rankings daily and watch exactly which metadata changes move the needle. Unlike most ASO tools under $50/mo, Sonar includes a full REST API and CLI with every subscription, so you can script keyword research across your whole app portfolio. Unlimited apps, unlimited keywords, both stores, daily rank tracking, competitor and keyword gap analysis, and review monitoring. $19/mo or $149/yr, with a 7-day full-access free trial. Free no-signup tools too: an ASO score checker and a keyword generator.