Apple has acquired indoor GPS company WifiSlam, according to a report by Jessica E. Lessin in The Wall Street Journal. The report says the deal was pegged at $20 million, quoting a person familiar with the matter. 

WifiSlam allows smartphones to pinpoint their location in real-time to 2.5m accuracy, using ambient WiFi signals that are already present in buildings. Applications range from step-by-step indoor navigation, to product-level retail customer engagement, to proximity-based social networking, says the company.

Investors in WifiSlam include Sky Dayton, Mareza Larizadeh, Naval Ravikant, Felix Shpilman, Don Dodge and Kevin Talbot, according to the company’s AngelList posting.